fix(684): review round 2 -- drop a false exhaustiveness claim I introduced

The L1 fix (name every class-b shape) collided with the M1 fix (move
SmartCollectionDialog into class-b) in the same commit: the comment claimed
"exactly three shapes, which is the whole list" while the registry 80 lines
below already held four. That is the same false-exhaustiveness defect this PR
exists to remove -- a reader adding a fifth class-b site would conclude theirs
cannot be class-b despite rendering a real totalCount hint, and reach for
search-bounded or deviation.

The operative rule is now stated first and the shape list is explicitly
illustrative: a site qualifies by RENDERING a totalCount-backed hint, not by
resembling a listed shape.

Also, both non-blocking review items:
- the deviation prose said the tracking issue goes "in the note", while
  enforcement is on the structural `issue` field -- it now points at the
  mechanism that actually binds, and says why the note scrape was rejected;
- the UNREGISTERED report prints every position sharing an identity, so it now
  says "identity seen at:" rather than implying all of them are unregistered. A
  positionless key cannot know which occurrence is excess; the candidate set is
  the honest answer.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

web/src/api/pageSizeCallSites.guard.test.ts

@@ -91,14 +91,21 @@ import { scanPageSizeSites } from './pageSizeScan';
  *                          NOT search-bounded (see 'deviation').
  *   - 'class-b'         — one bounded page at (or under) the cap, with the real truncation
  *                          (`totalCount` vs items shown) surfaced to the user. Post-#651 this no
- *                          longer covers media-library pickers (those are 'search-bounded'). It
- *                          remains correct for exactly three shapes, which is the whole list: a
- *                          list bounded by its PARENT (`ChannelBuilder`, seasons of one show); the
- *                          collection-family types §3b explicitly excludes from search
- *                          (`FillerPresetsScreen`), which keep the bounded page and its hint; and
- *                          a preview over an already-bounded set (`AutoTuneScreen`'s channel
- *                          members). Each of the three renders a real `totalCount`-backed hint —
- *                          that render is the entry requirement, not the intent.
+ *                          longer covers media-library pickers (those are 'search-bounded').
+ *                          **The RENDER is the entry requirement, not the intent** — that is the
+ *                          operative rule, and the only one to apply to a new site. Today's
+ *                          entries happen to take four shapes: a list bounded by its PARENT
+ *                          (`ChannelBuilder`, seasons of one show); the collection-family types
+ *                          §3b excludes from search (`FillerPresetsScreen`), which keep the
+ *                          bounded page and its hint; a preview over an already-bounded set
+ *                          (`AutoTuneScreen`'s channel members); and a preview over an UNBOUNDED
+ *                          user-authored query that surfaces its match count
+ *                          (`SmartCollectionDialog`). That list is illustrative and NOT
+ *                          exhaustive: a site qualifies by rendering a real `totalCount`-backed
+ *                          hint, not by resembling one of these four. (#684 review: an earlier
+ *                          revision of this comment called it "the whole list" while the registry
+ *                          below already held a fourth — the same false-exhaustiveness defect this
+ *                          PR exists to remove.)
  *   - 'paged-ui'        — real paging UI (a page/"load more" control, or a user-adjustable
  *                          page-size selector, keyed to a genuine `totalCount`), so a `pageSize`
  *                          at or below the cap is correct as-is.
@@ -106,9 +113,11 @@ import { scanPageSizeSites } from './pageSizeScan';
  *                          into a compliant-looking label. A registry exists to state what is
  *                          true; recording a defect as 'class-b' or 'search-bounded' would make
  *                          the guard assert a hint or a query gate that demonstrably does not
- *                          exist, and the next reader would trust it. Every such entry MUST name
- *                          its tracking issue in the note, and flips to a real class only when the
- *                          behaviour is fixed.
+ *                          exist, and the next reader would trust it. Every such entry MUST carry
+ *                          its tracking issue in the structural `issue` field — enforced below,
+ *                          and deliberately NOT a `#\d+` scrape of the note, which passed with the
+ *                          reference deleted because notes legitimately cite historical issues —
+ *                          and flips to a real class only when the behaviour is fixed.
  *
  * **Known residual gap:** object SPREAD (`getFoo({ ...opts })` where `opts` was built elsewhere
  * with an at-cap `pageSize`) and a `pageSize` passed as a bare POSITIONAL argument rather than an
@@ -419,7 +428,10 @@ function describeDiscovered(sites: DiscoveredSite[], ids: string[]): string[] {
   }
   return ids.map((id) => {
     const at = positions.get(id);
-    return at && at.length > 0 ? `${id}  (at ${at.join(', ')})` : id;
+    // Every position sharing this identity, not just the excess one: a positionless key genuinely
+    // cannot tell which occurrence is new, so the candidate set IS the honest answer. Labelled so a
+    // reader does not take all of them as unregistered (#684 review L-a).
+    return at && at.length > 0 ? `${id}  (identity seen at: ${at.join(', ')})` : id;
   });
 }