Implement live search filtering

The board's live title+body filter per 04-interactions.md § Search:

- SearchFilter — a pure value folding the query once (case- and
  diacritic-insensitive substring, locale-stable); title OR body matches,
  attachment filenames never searched; only the literal empty string is
  inactive.
- One universe: the filter threads through SelectionGrammar's order lists
  as a defaulted parameter, so ranges, Select All, arrow navigation, the
  marquee, drop zones, count badges, and the shown trash all read the same
  filtered set by construction; lanes are deliberately never filtered out
  (an emptied lane keeps its slot with a 0 badge). Hidden cards leave the
  selection through the existing constrain primitive, run on every query
  change and as the last line of the reload resolve; the delete successor
  is filtered so ⌫ never selects a hidden neighbour.
- The field: an NSSearchField-backed toolbar item (the toolbar's sole
  default item); Edit ▸ Find ⌘F focuses it through a focused-value
  presentation; stock field-editor dispatch — Return swallowed, Tab is the
  keep-filter path to the board, board commands stay enabled except the
  caret-chord pair, now one shared caretChordsYield expression.
- Escape is staged: clear the non-empty query (focus stays), hand an empty
  field back to the board, clear an active search from board focus —
  before Escape's clear-selection meaning.
- Creating a card clears the search (the placeholder funnel); a rename
  deliberately gets no carve-out; filter reflow rides the content spring
  keyed narrowly on the query.

903 unit tests (24 new).

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

Kanban/UI/Board/TrashLaneView.swift

@@ -34,8 +34,9 @@ import SwiftUI
 ///
 /// ### What is still a later card's
 ///
-/// The **search filter** ("shown, it participates in the filter like any lane") and **⌘C copy-out**
-/// are still owed. The *pointer* grammar is here: a row's click runs the same `SelectionGrammar` the
+/// **⌘C copy-out** is still owed. The **search filter** ("shown, it participates in the filter like
+/// any lane") arrived with m5 and is one line — see `entries`, which every other surface here reads
+/// through. The *pointer* grammar is here: a row's click runs the same `SelectionGrammar` the
 /// board does, and the column's empty space rubber-bands on the trashed side. So is the drop, with
 /// the target lane highlighted and the source row dimmed in place; the drag's replica is not. The
 /// **keyboard** reaches the column entirely through the frames the rows register — arrow walks in
@@ -83,11 +84,14 @@ struct TrashLaneView: View {
 
     /// The rows the column shows.
     ///
-    // m5-search: the shown trash "participates in the filter like any lane", so the search predicate
-    // narrows this collection exactly as it narrows `LaneView.renderedCards` — and the count badge
-    // follows for free, because it reads this same value.
+    /// **The shown trash "participates in the filter like any lane"** (03-board-ui.md § Trash), so
+    /// the search predicate narrows this collection exactly as it narrows `LaneView.renderedCards`
+    /// — card rows and lane rows alike, each by its own title and body (`SearchFilter`) — and the
+    /// count badge follows for free, because it reads this same value. Hidden, the column renders
+    /// nothing and registers nothing, so "hidden trash is invisible to search" needs no code at all.
     private var entries: [TrashEntry] {
-        TrashModel.entries(of: store.snapshot)
+        let filter = store.searchFilter
+        return TrashModel.entries(of: store.snapshot).filter { filter.matches($0) }
     }
 
     // MARK: - Header