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/LiveStore/TransientBoardState.swift

@@ -634,7 +634,13 @@ public final class TransientBoardState {
     /// on the freshly resolved sets, and the vanish rule and the filter rule compose in the one
     /// order that makes sense: gone first, then hidden. `isTrashVisible` is the only member with
     /// nothing to say here at all.
-    public func resolve(against snapshot: BoardModel) {
+    ///
+    /// - Parameter commentMatches: the transient comment index' current answer
+    ///   (`CommentSearchIndex.matchingCards`), threaded straight through to the constraint below.
+    ///   Defaulted, because it is the store's fact rather than this container's: everything else here
+    ///   is a rule about *this* state, and a caller with no index — every test of the resolution rules
+    ///   — means "no comment matches", which is what an empty set says.
+    public func resolve(against snapshot: BoardModel, commentMatches: Set<ItemID> = []) {
         selection = selection.resolved(against: snapshot)
         dragMembers = dragMembers.resolved(against: snapshot)
         pendingCut = pendingCut.resolved(against: snapshot)
@@ -661,7 +667,7 @@ public final class TransientBoardState {
             if let head = selectionHead, !universe.contains(head) { selectionHead = nil }
         }
 
-        constrainToSearch(in: snapshot)
+        constrainToSearch(in: snapshot, commentMatches: commentMatches)
     }
 
     /// **Hidden cards leave the selection** (04-interactions.md § Search) — the constraint rule with
@@ -692,8 +698,13 @@ public final class TransientBoardState {
     /// (`RenameEditor`) — read for the materialized trash, true container crossings — so a foreign
     /// edit that stops the renaming card matching drops it from the selection here and leaves the
     /// keystrokes exactly where the user left them.
-    public func constrainToSearch(in snapshot: BoardModel) {
-        let filter = SearchFilter(query: searchQuery)
+    /// **A third occasion joined the two** with the comment index (04 ▸ Search, re-ruled 2026-07-29):
+    /// a landed sweep can *widen* the visible universe (a card matching only through its comments
+    /// appears) and, on a re-sweep, narrow it again — so `CommentSearchIndex.onRefine` calls this too.
+    /// Widening constrains nothing, which is why the seam is worth having anyway: the narrowing half is
+    /// the one that would otherwise leave a selection on a card nobody can see.
+    public func constrainToSearch(in snapshot: BoardModel, commentMatches: Set<ItemID> = []) {
+        let filter = SearchFilter(query: searchQuery, commentMatches: commentMatches)
         guard filter.isActive else { return }
 
         let universe = filter.visibleIDs(in: snapshot, container: selection.container)