Comments, phase 3 — search, the thread find, announcements, and a11y

Board search reaches comment bodies through a search-owned transient
index: the first live-query keystroke sweeps comments/*/index.md
off-actor (.draft and comments/.trash excluded), keystrokes re-filter
in memory, the index discards on clear — the snapshot stays O(cards).
⌘F routes by focus: the comments pane gets an app-owned find bar
spanning the whole rendered thread (next/prev cross rows with
wraparound); body and composer keep NSTextFinder; Find Next/Previous
graduate from FutureCommands. Foreign comment changes speak
path-shaped beside the announcer's ladder ("New comment on 'X'",
plural folds), narrowed by EchoLedger receipts consumed through
CommentPath.classify — and that read fixed a latent footprint bug
where a comment receipt resolved against the card's attachment
listing, read .absent, and classified the user's own write as
foreign. The pane completes its a11y story: flattened comment
elements with Edit/Delete/Reveal custom actions (un-flattening
during inline edit), phrase-table vocabulary, labeled composer and
sort control, and an audit over the open pane on a comment-seeded
fixture (runnable only where automation permission exists).

Claude-Session: https://claude.ai/code/session_01SR4XGjmBE16ZUYWpfFHXwY

Kanban/App/CardWindowHost.swift

@@ -362,6 +362,11 @@ struct CardWindowHost: View {
                 attachments.cardFolder = folder
                 session.comments.cardFolder = folder
             }
+            // The announcer's subject, re-derived from every snapshot for the folder's reason: a card
+            // renamed mid-session is announced under its new name ("New comment on '⟨card⟩'").
+            .onChange(of: placement.card.title.value, initial: true) { _, title in
+                session.comments.cardTitle = title
+            }
             .onChange(of: store.isReadOnly, initial: true) { _, locked in
                 attachments.isEditable = !locked
                 session.comments.isEditable = !locked
@@ -372,13 +377,15 @@ struct CardWindowHost: View {
             // *Any* reload, not a filtered one, and that is a deliberate choice worth stating: the
             // store's observable surface publishes `snapshotGeneration` and a `BoardModel` — it does
             // not vend the changed paths, and comments are outside the snapshot entirely
-            // (01-storage-format.md § Enhanced schema), so there is nothing here to run
-            // `CommentPath.classify` against. Re-reading one card's thread is a handful of small
-            // files and happens only while a card window is open; filtering would mean either
-            // widening the store's surface to carry paths, or the pane keeping its own watcher — a
-            // second stream over the same tree, which the one-way flow rules out. `initial:` is
-            // deliberately absent: `start()` already did the opening read, after the residue sweep
-            // that has to precede it.
+            // (01-storage-format.md § Enhanced schema), so there is nothing to filter *on* here.
+            // Re-reading one card's thread is a handful of small files and happens only while a card
+            // window is open; filtering would mean either widening the store's surface to carry paths,
+            // or the pane keeping its own watcher — a second stream over the same tree, which the
+            // one-way flow rules out. The path shape is read on the other side of the re-read instead,
+            // where there *are* two pictures to compare: the pane diffs its threads and consumes the
+            // ledger's comment receipts through `CommentPath.classify` to tell a foreign arrival from
+            // its own echo (`CardComments.reload`). `initial:` is deliberately absent: `start()`
+            // already did the opening read, after the residue sweep that has to precede it.
             .onChange(of: store.snapshotGeneration) { _, _ in
                 session.comments.reload()
             }
@@ -577,6 +584,13 @@ struct CardWindowHost: View {
         comments.composer.post = { [weak store] in
             store?.postComment(inCard: cardID)
         }
+        // The announcer's gate: which of this thread's changes the app itself wrote, consumed once per
+        // reload (10-accessibility.md — "app-mediated echoes never announce", per comment). A store
+        // that has gone vouches for nothing, which is the conservative direction and also the one the
+        // announcement cannot reach anyway — a released store has no window left to speak in.
+        comments.vouchedComments = { [weak store] in
+            store?.vouchedComments(inCard: cardID) ?? []
+        }
     }
 
     /// Points the attachments section at its card — **the one place Add Attachment… and Remove