feat(family): platforms declared at inception and detected from bound repos (milestone 463 step 2, #4988)

A project's platforms decide which family ideas reach it. This step makes membership answerable from every door:

- services/platforms.py: the global catalog (writes are admin-only and duplicate-gated by slug); pure marker detection; and membership reads and writes. Detection only ADDS, and only where nobody has answered. It never overrides a declared or rejected row and never removes one.
- coverage: the archive scan now carries every path, and the refresh runs detection fail-open.
- inception: a platforms choice (slugs, or null for unanswered). The list is the whole answer: members left out of it become rejected.
- MCP: list_platforms and set_project_platforms; enter_project and get_project carry the project's platforms.
- REST: /api/platforms (admin writes) and /api/projects/<id>/platforms.
- UI: a platforms checklist on the inception card, a Family tab on ProjectView, and a Platforms admin tab in Settings.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/views/ProjectView.vue

@@ -12,6 +12,8 @@ import KindBadge from "@/components/KindBadge.vue";
 import ProjectStatusBadge from "@/components/ProjectStatusBadge.vue";
 import type { TaskKind } from "@/types/note";
 import ProjectDesignTab from "@/components/ProjectDesignTab.vue";
+import ProjectFamilyTab from "@/components/ProjectFamilyTab.vue";
+import { canWriteRecord } from "@/utils/permission";
 import ProjectRulesTab from "@/components/rules/ProjectRulesTab.vue";
 import SystemsSection from "@/components/SystemsSection.vue";
 import InceptionCard from "@/components/InceptionCard.vue";
@@ -125,7 +127,7 @@ async function confirmStartPlanning() {
 const saving = ref(false);
 const error = ref<string | null>(null);
 
-const activeTab = ref<"tasks" | "notes" | "systems" | "rules" | "design">("tasks");
+const activeTab = ref<"tasks" | "notes" | "systems" | "rules" | "design" | "family">("tasks");
 
 const tasks = ref<NoteItem[]>([]);
 const notes = ref<NoteItem[]>([]);
@@ -747,6 +749,10 @@ async function confirmDelete() {
         Inheritance decided {{ fmtDate(project.inception.decided_at) }} via {{ project.inception.via }}
         · design system {{ project.inception.choices.design_system_id ? "#" + project.inception.choices.design_system_id : "none" }}
         <template v-if="project.inception.choices.seed_systems"> · Systems seeded</template>
+        <!-- What was said AT inception; the live answers are on the Family tab. -->
+        <template v-if="project.inception.choices.platforms?.length">
+          · platforms {{ project.inception.choices.platforms.join(", ") }}
+        </template>
       </p>
 
       <!-- Summary stat chips -->
@@ -945,6 +951,9 @@ async function confirmDelete() {
             <button :class="['tab-btn', { active: activeTab === 'design' }]" @click="activeTab = 'design'">
               Design
             </button>
+            <button :class="['tab-btn', { active: activeTab === 'family' }]" @click="activeTab = 'family'">
+              Family
+            </button>
           </div>
 
           <!-- Tasks tab — milestone-grouped kanban -->
@@ -1190,6 +1199,13 @@ async function confirmDelete() {
             :project-id="projectId"
             :design-system-id="project.design_system_id ?? null"
           />
+
+          <!-- Family tab (milestone 463): which platforms this project is. -->
+          <ProjectFamilyTab
+            v-if="activeTab === 'family'"
+            :project-id="projectId"
+            :can-write="canWriteRecord(project.permission)"
+          />
         </div>
       </div>
     </template>

frontend/src/views/SettingsView.vue

@@ -4,6 +4,7 @@ import { useSettingsStore } from "@/stores/settings";
 import { useAuthStore } from "@/stores/auth";
 import { useToastStore } from "@/stores/toast";
 import { useCanonicalSystemsStore } from "@/stores/canonicalSystems";
+import { usePlatformsStore } from "@/stores/platforms";
 import { apiGet, apiPost, apiPut, apiDelete, listGroups, createGroup, deleteGroup, listGroupMembers, addGroupMember, removeGroupMember, searchUsers, listApiKeys, createApiKey as apiCreateApiKey, revokeApiKey as apiRevokeApiKey, getProfile, updateProfile, type ApiKeyEntry, type GroupEntry, type GroupMember, type UserSearchResult, type UserProfile, apiErrorMessage } from "@/api/client";
 import type { User } from "@/types/auth";
 import PaginationBar from "@/components/PaginationBar.vue";
@@ -71,6 +72,75 @@ async function saveArea() {
     savingArea.value = false;
   }
 }
+// ── Platforms (milestone 463) ───────────────────────────────────────────
+// The global list of what a project can be built on or ship as. Same split
+// as the areas: admin-only to write, readable by everyone. Markers are the
+// repo-relative globs that let a coverage refresh DETECT a platform; they
+// are edited one per line, since a glob may itself contain a comma.
+const platformsStore = usePlatformsStore();
+const newPlatformName = ref("");
+const newPlatformDescription = ref("");
+const newPlatformMarkers = ref("");
+const creatingPlatform = ref(false);
+const editingPlatformId = ref<number | null>(null);
+const editPlatformName = ref("");
+const editPlatformDescription = ref("");
+const editPlatformMarkers = ref("");
+const savingPlatform = ref(false);
+
+function markerLines(text: string): string[] {
+  return text.split("\n").map((m) => m.trim()).filter(Boolean);
+}
+
+async function createPlatform() {
+  const name = newPlatformName.value.trim();
+  if (!name || creatingPlatform.value) return;
+  creatingPlatform.value = true;
+  try {
+    await platformsStore.createEntry({
+      name,
+      description: newPlatformDescription.value.trim() || undefined,
+      markers: markerLines(newPlatformMarkers.value),
+    });
+    newPlatformName.value = "";
+    newPlatformDescription.value = "";
+    newPlatformMarkers.value = "";
+    toastStore.show("Platform added");
+  } catch (e) {
+    // A 409 names the existing platform the new name reduces to.
+    toastStore.show(apiErrorMessage(e, "Failed to add platform"), "error");
+  } finally {
+    creatingPlatform.value = false;
+  }
+}
+
+function startEditPlatform(id: number, name: string, description: string | null, markers: string[]) {
+  editingPlatformId.value = id;
+  editPlatformName.value = name;
+  editPlatformDescription.value = description ?? "";
+  editPlatformMarkers.value = markers.join("\n");
+}
+
+async function savePlatform() {
+  const id = editingPlatformId.value;
+  const name = editPlatformName.value.trim();
+  if (id == null || !name || savingPlatform.value) return;
+  savingPlatform.value = true;
+  try {
+    await platformsStore.updateEntry(id, {
+      name,
+      description: editPlatformDescription.value.trim(),
+      markers: markerLines(editPlatformMarkers.value),
+    });
+    editingPlatformId.value = null;
+    toastStore.show("Platform updated");
+  } catch (e) {
+    toastStore.show(apiErrorMessage(e, "Failed to update platform"), "error");
+  } finally {
+    savingPlatform.value = false;
+  }
+}
+
 const userTimezone = ref("");
 const savingTimezone = ref(false);
 const timezoneSaved = ref(false);
@@ -479,7 +549,7 @@ async function copyCommit() {
 const restoreFileInput = ref<HTMLInputElement | null>(null);
 
 // Migrate stored "admin" → "config"; unknown tabs fall back to "general"
-const VALID_TABS = new Set(["general", "account", "profile", "notifications", "integrations", "data", "apikeys", "config", "users", "logs", "groups", "areas"]);
+const VALID_TABS = new Set(["general", "account", "profile", "notifications", "integrations", "data", "apikeys", "config", "users", "logs", "groups", "areas", "platforms"]);
 const _stored = localStorage.getItem("settings_tab") ?? "general";
 const activeTab = ref(VALID_TABS.has(_stored) ? (_stored === "admin" ? "config" : _stored) : "general");
 
@@ -489,6 +559,7 @@ function _loadTabContent(tab: string) {
     else if (tab === "logs") loadLogsPanel();
     else if (tab === "groups") loadGroupsPanel();
     else if (tab === "areas") canonStore.fetchCatalog(true);
+    else if (tab === "platforms") platformsStore.fetchCatalog(true);
     else if (tab === "config" && !versionInfo.value) loadVersionPanel();
   }
   if (tab === "apikeys") { fetchApiKeys(); }
@@ -1611,7 +1682,7 @@ async function deleteUser(userId: number) {
       <div v-if="authStore.isAdmin" class="sidebar-group">
         <div class="sidebar-group-label">Admin</div>
         <button
-          v-for="tab in ['config', 'areas', 'users', 'groups', 'logs']"
+          v-for="tab in ['config', 'areas', 'platforms', 'users', 'groups', 'logs']"
           :key="tab"
           :class="['sidebar-item', { active: activeTab === tab }]"
           @click="activeTab = tab"
@@ -3179,6 +3250,99 @@ async function deleteUser(userId: number) {
       </section>
     </div>
 
+    <!-- ── Platforms ── -->
+    <div v-if="authStore.isAdmin" v-show="activeTab === 'platforms'" class="settings-grid">
+      <section class="settings-section full-width">
+        <h2>Platforms</h2>
+        <p class="field-hint">
+          What a project can be built on or ship as. A project's platforms decide which family
+          ideas reach it. Markers are repo-relative file patterns, one per line: a bare name
+          (<code>go.mod</code>) matches that file anywhere in a bound repo, and a pattern with a
+          slash (<code>.github/workflows/*</code>) matches the whole path. A platform with no
+          markers is never detected — projects declare it themselves.
+        </p>
+
+        <ul class="area-admin-list">
+          <li v-for="entry in platformsStore.catalog" :key="entry.id" class="area-admin-row">
+            <template v-if="editingPlatformId === entry.id">
+              <form class="area-admin-form" @submit.prevent="savePlatform">
+                <input v-model="editPlatformName" class="fs-input" aria-label="Platform name" />
+                <textarea
+                  v-model="editPlatformDescription"
+                  class="fs-input"
+                  rows="2"
+                  aria-label="Platform description"
+                ></textarea>
+                <textarea
+                  v-model="editPlatformMarkers"
+                  class="fs-input area-admin-markers"
+                  rows="3"
+                  aria-label="Detection markers, one per line"
+                ></textarea>
+                <div class="area-admin-actions">
+                  <button type="submit" class="btn-primary btn-compact" :disabled="!editPlatformName.trim() || savingPlatform">
+                    {{ savingPlatform ? "Saving…" : "Save" }}
+                  </button>
+                  <button type="button" class="btn-ghost btn-compact" @click="editingPlatformId = null">Cancel</button>
+                </div>
+              </form>
+            </template>
+            <template v-else>
+              <div class="area-admin-body">
+                <div class="area-admin-name-row">
+                  <span class="area-admin-name">{{ entry.name }}</span>
+                  <code class="area-admin-slug" title="The match key, and the name tools and backups use.">{{ entry.slug }}</code>
+                </div>
+                <p v-if="entry.description" class="area-admin-desc">{{ entry.description }}</p>
+                <p class="area-admin-desc">
+                  <template v-if="entry.markers.length">
+                    Detected by
+                    <code v-for="m in entry.markers" :key="m" class="area-admin-slug">{{ m }}</code>
+                  </template>
+                  <template v-else>Declare-only — never detected.</template>
+                </p>
+              </div>
+              <button
+                class="btn-ghost btn-compact"
+                @click="startEditPlatform(entry.id, entry.name, entry.description, entry.markers)"
+              >Edit</button>
+            </template>
+          </li>
+        </ul>
+        <p v-if="!platformsStore.catalog.length && !platformsStore.loading" class="settings-empty">
+          No platforms yet.
+        </p>
+
+        <form class="area-admin-form area-admin-create" @submit.prevent="createPlatform">
+          <input
+            v-model="newPlatformName"
+            class="fs-input"
+            placeholder="New platform name (e.g. Flutter app)"
+            aria-label="New platform name"
+          />
+          <textarea
+            v-model="newPlatformDescription"
+            class="fs-input"
+            rows="2"
+            placeholder="What makes a project this platform? One sentence."
+            aria-label="New platform description"
+          ></textarea>
+          <textarea
+            v-model="newPlatformMarkers"
+            class="fs-input area-admin-markers"
+            rows="2"
+            placeholder="Markers, one per line (e.g. pubspec.yaml) — leave empty for declare-only"
+            aria-label="New platform markers, one per line"
+          ></textarea>
+          <div class="area-admin-actions">
+            <button type="submit" class="btn-primary btn-compact" :disabled="!newPlatformName.trim() || creatingPlatform">
+              {{ creatingPlatform ? "Adding…" : "Add platform" }}
+            </button>
+          </div>
+        </form>
+      </section>
+    </div>
+
     <div v-if="authStore.isAdmin" v-show="activeTab === 'users'" class="settings-grid">
 
       <section class="settings-section full-width">
@@ -4386,6 +4550,8 @@ async function deleteUser(userId: number) {
 .area-admin-form { display: flex; flex-direction: column; gap: 0.5rem; flex: 1; }
 .area-admin-create { margin-top: var(--fs-space-4); }
 .area-admin-actions { display: flex; gap: 0.4rem; }
+.area-admin-markers { font-family: var(--fs-font-mono); font-size: 0.82rem; }
+.area-admin-desc .area-admin-slug { margin-right: 0.25rem; }
 
 /* The retrieval tuning trail (#4102). Reads as a record, not a control panel:
    the operator is reviewing what was done, and the reason is the part worth