docs(tiles): the tile grid in CLAUDE.md, the invariants, the wiki and the Help modal

- CLAUDE.md: a Tile grid paragraph beside the split-pane one (parking, the
  one load queue, the selection and close rules, chords, dividers, auto-join,
  the exited-agent case), tile-grid.js (7.6) in the load order, the
  desktop-gated header markers and the Tiles picker in the z-index stack.
- docs/architecture-invariants.md#tile-grid: the mechanisms and the reason
  behind each rule; the split section now says where a waiting grid load
  differs and that every capture carries a deadline.
- docs/wiki/Tile-Grid.md: the user manual page (turning it on, the ways in, a
  tile's header, keys, leaving, persistence, Split), linked from the sidebar,
  The Dashboard, Keyboard Shortcuts and Settings Reference.
- The Help modal lists the tile chords (pinned in help-modal-shortcuts.test).
- docs/tile-grid-plan.md: status updated, and an "as built" list of where PR 2
  went another way than the spec.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/wiki/Settings-Reference.md

@@ -57,7 +57,7 @@ supervised by systemd or launchd; npm installs report as non-updatable. See
 Chips for every optional header control, with a live preview of the resulting header:
 
 Run, Font Size, System Stats, Redraw Terminal, Response Viewer, Away Digest, Session
-Manager, Attachments, File Viewer, Multi-monitor, Split, Plan Usage, Lifecycle Log, Monitor,
+Manager, Attachments, File Viewer, Multi-monitor, Split, Tiles, Plan Usage, Lifecycle Log, Monitor,
 Project Insights, File Browser, Subagents, Approvals Inbox, Read My Mind, Ultracode Agents,
 Ultracode Windows, Cron.
 
@@ -71,7 +71,9 @@ window; off lists every file by its full path.
 Most default to off. The stock desktop header is system stats, File Viewer, and the gear.
 New header controls never appear on phones. Split is desktop-only regardless of this
 setting — the button and the feature both stay off below a ~1180px viewport, where two
-resizable panes plus their divider have nowhere to go.
+resizable panes plus their divider have nowhere to go. **Tiles** is desktop-only the same
+way; it also enables the `Ctrl+Shift+G` grid toggle on this device. See
+[Tile Grid](Tile-Grid).
 
 This section also holds background-agent tracking, including whether to track agents for
 every session or only the active tab.