feat(rules)!: retire rulebook subscriptions and per-project suppressions (#4052)

A rule's home is its scope now: a rule in a rulebook topic is global, a rule on
a project applies to that project, and retrieval reads that directly (#4074).
A subscription had stopped changing anything a session received; a suppression
muted rules from a subscription. Operator, 2026-09-15: "we have global and
project scoped rules, we don't need the subscriptions now."

What goes, whole (rule 22):
- Migration 0101 drops project_rulebook_subscriptions, project_rule_suppressions
  and project_topic_suppressions, and strips subscribe_rulebooks (and 394's
  leftover exclude_always_on_rulebooks) from stored inception choices.
- Service, MCP and REST: subscribe/unsubscribe and the four suppress/unsuppress
  operations. The Subscribers checklist, the subscribe chips, the skip buttons
  and the Suppressed section in the rules UI.
- Inception asks two questions (design system, seed Systems). create_project and
  decide_project_inception lose subscribe_rulebooks.
- Backup v15 stops exporting the three sections; older archives still restore,
  the keys simply unread. Trash no longer hard-deletes suppression rows.

What changes meaning:
- get_applicable_rules is a project's LISTING: its own rules, plus the global
  rules tagged to an area it works in. Untagged global rules apply everywhere
  and arrive by retrieval, so they are not listed. A co_surfaces partner on a
  different project is not dragged in.
- list_rules(project_id) lists that project's own rules.
- rules_payload drops subscribed_rulebooks and suppressed_*; the handshake's
  brief form is project_rules alone.
- using-scribe's "Where a new rule goes" and inception sections, tool
  docstrings and docs say global vs project. Plugin 2026.09.15.1620.

Milestone 414 step 2.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01821k5B3Ysecp9fNYs92Kuy

frontend/src/components/InceptionCard.vue

@@ -14,7 +14,6 @@ import {
   decideInception, emptyChoices, fetchInceptionDefaults,
   type InceptionChoices, type InceptionDecision, type InceptionDefaults,
 } from "@/api/inception";
-import { listRulebooks } from "@/api/rulebooks";
 
 const props = withDefaults(defineProps<{
   mode: "create" | "decide";
@@ -28,7 +27,6 @@ const emit = defineEmits<{
 }>();
 
 const local = ref<InceptionChoices>(props.choices ? { ...props.choices } : emptyChoices());
-const others = ref<{ id: number; title: string }[]>([]);
 const designSystems = ref<{ id: number; title: string }[]>([]);
 const systemsCount = ref(0);
 const loading = ref(true);
@@ -46,18 +44,12 @@ async function load() {
   try {
     if (props.mode === "decide" && props.projectId) {
       const d: InceptionDefaults = await fetchInceptionDefaults(props.projectId);
-      others.value = d.rulebooks;
       designSystems.value = d.design_systems;
       systemsCount.value = d.systems;
-      // Start from what stands today so "record" without changes is a true inherit-all.
-      local.value = {
-        subscribe_rulebooks: d.subscribed_rulebooks.map((r) => r.id),
-        design_system_id: d.design_system_id,
-        seed_systems: false,
-      };
+      // Start from what stands today, so "record" without changes keeps it.
+      local.value = { design_system_id: d.design_system_id, seed_systems: false };
     } else {
-      const [rulebooks, ds] = await Promise.all([listRulebooks(), fetchDesignSystems()]);
-      others.value = rulebooks.map((r) => ({ id: r.id, title: r.title }));
+      const ds = await fetchDesignSystems();
       designSystems.value = ds.design_systems.map((d) => ({ id: d.id, title: d.title }));
     }
   } catch (e: unknown) {
@@ -67,17 +59,7 @@ async function load() {
   }
 }
 
-function subscribed(id: number): boolean {
-  return local.value.subscribe_rulebooks.includes(id);
-}
-function toggleSubscribe(id: number) {
-  const list = local.value.subscribe_rulebooks;
-  local.value.subscribe_rulebooks = list.includes(id) ? list.filter((x) => x !== id) : [...list, id];
-}
-
-const nothingToDecide = computed(
-  () => !others.value.length && !designSystems.value.length,
-);
+const nothingToDecide = computed(() => !designSystems.value.length);
 
 async function record() {
   if (!props.projectId) return;
@@ -101,22 +83,12 @@ onMounted(load);
     <h3 id="inception-title" class="inception-title">What does this project inherit?</h3>
     <p class="inception-lede">
       A project's inheritance is a decision, not a default. Until it is recorded,
-      every always-on rulebook binds, nothing is subscribed, and there is no design
-      system or Systems.
+      there is no design system and no Systems. Rules aren't part of this: global
+      rules apply to every project, and a project's own rules are added on it.
     </p>
     <p v-if="loading" class="inception-muted">Loading…</p>
     <p v-else-if="error" class="error-msg">{{ error }}</p>
     <template v-else>
-      <div v-if="others.length" class="inception-group">
-        <h4>Subscribe to rulebooks</h4>
-        <p class="inception-muted">
-          A rulebook binds this project only if it is subscribed — nothing is inherited automatically.
-        </p>
-        <label v-for="rb in others" :key="rb.id" class="inception-choice">
-          <input type="checkbox" :checked="subscribed(rb.id)" @change="toggleSubscribe(rb.id)" />
-          <span>{{ rb.title }}</span>
-        </label>
-      </div>
       <div class="inception-group">
         <h4>Design system</h4>
         <select v-model="local.design_system_id" class="inception-select" aria-label="Design system">
@@ -134,7 +106,7 @@ onMounted(load);
         </label>
       </div>
       <p v-if="nothingToDecide" class="inception-muted">
-        Nothing to inherit yet on this install — recording still settles the question.
+        No design systems on this install yet — recording still settles the question.
       </p>
       <div v-if="mode === 'decide'" class="inception-actions">
         <button class="btn-primary" :disabled="saving" @click="record">