fix(usage): one seam attaches the surfaced-vs-opened chip, and the Knowledge browse uses it (#4230)

`usage_for_notes` is named for notes and works on every note row, yet the chip
reached snippets and rules only. Notes had it nowhere. Lessons had it collected
and shown nowhere a person could reach, because #4196 taught `/api/lessons` to
attach it and `KnowledgeView` — the only lesson list in the UI — browses through
`/api/knowledge`, so `listLessons` still has no consumer.

The cause was not a missing line. SEVEN call sites carried their own copy of the
same few lines: two REST lists, two REST details, two MCP lists, one MCP detail.
Each read perfectly well alone, so "which doors attach usage?" had no answer
anywhere in the code — the same asymmetry test_system_tagging_door_parity.py
records for System tagging (#4249), where whichever door nobody exercised for a
kind is the one that never grew the feature.

`attach_usage(rows, key="id")` is now that answer, and all seven go through it.
A detail payload is a one-row list, so the single-record doors share the seam
rather than keeping a second shape beside it. Deliberately NO try/except: the
fail-open already lives in `usage_for_notes`, which reports through
`_report_failure("readout")` and returns the zero-filled map. Wrapping it again
would swallow the REPORT as well as the error, and a silently-swallowed readout
failure is exactly #2663 — every counter reading zero in production for weeks
while the writes landed fine.

`/api/knowledge` now attaches usage, which closes both holes at once: it is how
notes, lessons and processes are all browsed. `KnowledgeView` renders the badge
on the card footer, looking the advice up per row because the feed is mixed.

The advice moves to utils/deadWeight.ts. Canon #3460 says each caller owns its
own const, and that held while each caller showed ONE kind; a mixed feed would
need five of its own and the next surface another five. The canon's actual
invariant — advice is kind-specific and never baked into the badge — is kept:
it is still a prop. The three existing callers now read the same table, so the
sentence has one home rather than four. Recorded against #3460 so the next
reader is not left re-litigating it.

`_row_id` rejects bools explicitly: `int(True)` is 1, so a row carrying a flag
under the key would be credited with note #1's counts, and a wrong chip is worse
than no chip because it reads as a measurement. A row with no usable id is
skipped rather than failing the page.

Tests pin the PROPERTY, not one route: no door calls the aggregate directly
(AST, so a comment naming it is not a false positive), and every door that shows
usage reaches the seam. Plus the N+1 guard — one aggregate per page, asserted on
await_count, because the per-row version reads more naturally and is invisible
in review.

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

frontend/src/components/rules/RuleListPane.vue

@@ -1,16 +1,7 @@
 <script setup lang="ts">
 import type { RuleHeader } from "@/api/rulebooks";
 import UsageBadge from "@/components/UsageBadge.vue";
-
-/** The dead-weight nudge for a RULE — two remedies, not one, which is the
- *  whole reason this advice is per-kind. A snippet nobody opens should
- *  probably go. A rule nobody opens may be perfectly good and simply firing on
- *  the wrong thing, so "delete it" would be the wrong nudge half the time and
- *  the operator has to be the one who picks. */
-const RULE_DEAD_WEIGHT =
-  "Kept arriving without being read. Either its trigger fires on the wrong " +
-  "work — reword “when to apply” so it says when — or it is not wanted here. " +
-  "Until one or the other, it takes a slot in every write it matches.";
+import { DEAD_WEIGHT_ADVICE } from "@/utils/deadWeight";
 
 defineProps<{ topicId: number; rules: RuleHeader[] }>();
 const emit = defineEmits<{
@@ -54,7 +45,7 @@ const emit = defineEmits<{
               ? 'Asserts a fact nobody has confirmed yet'
               : `Check last passed ${r.last_verified}`"
           >{{ r.last_verified === "never" ? "unverified" : `checked ${r.last_verified}` }}</span>
-          <UsageBadge :usage="r.usage" :dead-weight-advice="RULE_DEAD_WEIGHT" />
+          <UsageBadge :usage="r.usage" :dead-weight-advice="DEAD_WEIGHT_ADVICE.rule" />
         </div>
         <div class="statement">{{ r.statement }}</div>
         <div v-if="r.when_to_apply || r.updated_at" class="meta">

frontend/src/utils/deadWeight.ts

@@ -0,0 +1,68 @@
+/**
+ * What to suggest when a record looks like dead weight — one sentence per kind.
+ *
+ * `UsageBadge` deliberately takes the advice as a prop rather than deriving it,
+ * because the COUNTS read identically for every kind and the REMEDY does not: a
+ * snippet nobody opens should probably go, while a rule or a lesson in the same
+ * position more often has a trigger that fires on the wrong work. Telling an
+ * operator to delete one of those would be the wrong nudge about half the time.
+ *
+ * The table lives here because the copy was about to exist in five places.
+ * Three already had their own: `SnippetListView`, `RuleListPane`, and
+ * `LessonDetailView` with the sentence inline in its template. The unified
+ * Knowledge browse renders notes, tasks, processes, snippets and lessons in one
+ * mixed feed (#4230), so it needs all of them at once — and a per-view constant
+ * is how three surfaces end up giving three different answers to the same
+ * question.
+ *
+ * Every sentence names the COST of leaving it, not just the fact. "Never
+ * opened" is an observation; "takes a slot in every future menu" is why the
+ * reader should care, and it is the half that makes the chip actionable.
+ */
+
+/** The record kinds the Knowledge feed can show, plus the ones only their own
+ *  views show. Keyed by `note_type`, with `rule` alongside — rules live in a
+ *  separate table but answer the same question (see `RecordUsage`). */
+export type DeadWeightKind =
+  | "note"
+  | "task"
+  | "process"
+  | "snippet"
+  | "lesson"
+  | "rule";
+
+export const DEAD_WEIGHT_ADVICE: Record<DeadWeightKind, string> = {
+  snippet:
+    "Offered repeatedly without ever being opened — consider rewriting its " +
+    "“when to reach for it” so it says when, or deleting it. It takes a slot " +
+    "in every future auto-inject menu.",
+  rule:
+    "Kept arriving without being read. Either its trigger fires on the wrong " +
+    "work — reword “when to apply” so it says when — or it is not wanted here. " +
+    "Until one or the other, it takes a slot in every write it matches.",
+  lesson:
+    "Repeatedly offered and never opened usually means the trigger fires on " +
+    "the wrong situation — re-key `when_to_apply` rather than deleting the " +
+    "claim.",
+  note:
+    "Surfaced again and again and never opened. Usually the title is the " +
+    "problem: recall matches on it first, so a note titled for its author " +
+    "rather than for the situation keeps winning slots it cannot pay for.",
+  process:
+    "Offered without ever being run. Either the steps no longer match how " +
+    "the work is actually done, or it is being matched on the wrong trigger " +
+    "— check which before retiring it.",
+  task:
+    "Surfaced repeatedly and never opened. On a task this more often says " +
+    "the work has gone stale than that the record is wrong — decide whether " +
+    "it is still wanted before re-titling it.",
+};
+
+/** The advice for a kind, falling back to the note wording.
+ *
+ * The fallback is deliberate rather than an empty string: a kind added to the
+ * feed later should still get a usable sentence, and "the title is doing the
+ * matching" is the reading that holds for any record recall can choose. */
+export function deadWeightAdvice(kind: string | null | undefined): string {
+  return DEAD_WEIGHT_ADVICE[kind as DeadWeightKind] ?? DEAD_WEIGHT_ADVICE.note;
+}

frontend/src/views/KnowledgeView.vue

@@ -3,7 +3,10 @@ import { ref, computed, watch, onMounted, onUnmounted, nextTick } from "vue";
 import { useRouter } from "vue-router";
 import { apiGet } from "@/api/client";
 import type { TaskKind, TaskStatus, TaskPriority } from "@/types/note";
+import type { RecordUsage } from "@/types/usage";
+import { deadWeightAdvice } from "@/utils/deadWeight";
 import KindBadge from "@/components/KindBadge.vue";
+import UsageBadge from "@/components/UsageBadge.vue";
 import NoteSweepPane from "@/components/NoteSweepPane.vue";
 import StatusBadge from "@/components/StatusBadge.vue";
 import PriorityBadge from "@/components/PriorityBadge.vue";
@@ -44,6 +47,10 @@ interface KnowledgeItem {
   project_id: number | null;
   created_at: string;
   updated_at: string;
+  /** Surfaced-vs-opened counts, zero-filled by the route for EVERY row, so
+   *  "never surfaced" is a value here rather than a missing field (#4230).
+   *  `UsageBadge` renders nothing at all below one surfacing. */
+  usage?: RecordUsage | null;
   // Set only when another user owns this record — their suggestion, not one of
   // yours. Absent means it's yours.
   shared?: boolean;
@@ -659,6 +666,16 @@ onUnmounted(() => {
                 class="shared-tag"
                 :title="`Shared by ${item.owner ?? 'another user'} — their record, not yours`"
               >by {{ item.owner ?? "another user" }}</span>
+              <!-- Surfaced-vs-opened (#4230). This is the only list in the UI
+                   that browses notes and lessons, so it is the only place
+                   those two kinds can show the counter at all. The advice is
+                   looked up per row because this feed is mixed — the remedy
+                   for a snippet nobody opens is not the remedy for a lesson. -->
+              <UsageBadge
+                :usage="item.usage"
+                :noun="item.note_type"
+                :dead-weight-advice="deadWeightAdvice(item.note_type)"
+              />
               <span class="k-card-date">{{ formatDate(item.updated_at) }}</span>
             </div>
           </div>

frontend/src/views/LessonDetailView.vue

@@ -25,6 +25,7 @@ import { deleteLesson, getLesson, type Lesson } from "@/api/lessons";
 import ConfirmDialog from "@/components/ConfirmDialog.vue";
 import TagPill from "@/components/TagPill.vue";
 import UsageBadge from "@/components/UsageBadge.vue";
+import { DEAD_WEIGHT_ADVICE } from "@/utils/deadWeight";
 import { useToastStore } from "@/stores/toast";
 import { renderMarkdown } from "@/utils/markdown";
 
@@ -110,7 +111,7 @@ onMounted(load);
         <UsageBadge
           :usage="lesson.usage"
           noun="lesson"
-          dead-weight-advice="Repeatedly offered and never opened usually means the trigger fires on the wrong situation — re-key `when_to_apply` rather than deleting the claim."
+          :dead-weight-advice="DEAD_WEIGHT_ADVICE.lesson"
         />
       </div>
 

frontend/src/views/SnippetListView.vue

@@ -10,6 +10,7 @@ import {
 } from "@/api/snippets";
 import { useToastStore } from "@/stores/toast";
 import UsageBadge from "@/components/UsageBadge.vue";
+import { DEAD_WEIGHT_ADVICE } from "@/utils/deadWeight";
 
 const router = useRouter();
 const toast = useToastStore();
@@ -237,14 +238,6 @@ function driftTitle(s: SnippetListItem): string {
   const what = reasons[v.status] ?? "";
   return v.detail ? `${when}: ${what}. ${v.detail}` : `${when}: ${what}.`;
 }
-
-/** The dead-weight nudge for a SNIPPET, passed to the shared badge. Kept here
- *  rather than inside the component because the remedy is kind-specific — a
- *  rule in the same position gets different advice (milestone 333 step 5). */
-const SNIPPET_DEAD_WEIGHT =
-  "Offered repeatedly without ever being opened — consider rewriting its " +
-  "“when to reach for it” so it says when, or deleting it. It takes a slot " +
-  "in every future auto-inject menu.";
 </script>
 
 <template>
@@ -431,7 +424,7 @@ const SNIPPET_DEAD_WEIGHT =
           <span v-if="driftBadge(s)" class="drift-tag" :title="driftTitle(s)">
             {{ driftBadge(s) }}
           </span>
-          <UsageBadge :usage="s.usage" :dead-weight-advice="SNIPPET_DEAD_WEIGHT" />
+          <UsageBadge :usage="s.usage" :dead-weight-advice="DEAD_WEIGHT_ADVICE.snippet" />
           <span v-if="s.shared" class="shared-tag" :title="`Shared by ${s.owner ?? 'another user'} — a suggestion, not your own record`">
             by {{ s.owner ?? "another user" }}
           </span>