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/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>