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/Keyboard-Shortcuts.md

@@ -39,6 +39,19 @@ from its tab, or bind a key to it in App Settings → Shortcuts.
 
 Anything you copy is cleaned on the way to the clipboard: each line loses the padding spaces a full-screen program paints across the rest of the row. Leading indentation is left exactly as it is, so indented code, a `git log` message body and `git diff` context lines paste back the way they looked on screen. An `Alt+drag` rectangular selection is copied exactly as it looks, so its columns stay lined up.
 
+## Tile grid
+
+| Shortcut                    | Action                                                       |
+| --------------------------- | ------------------------------------------------------------ |
+| `Ctrl+Shift+G`              | Open or close the tile grid (needs the Tiles setting on).     |
+| `Alt+Shift+Arrows`          | Focus the tile to the left, right, above or below.            |
+| `Alt+Shift+Enter`           | Zoom the focused tile, or restore the grid.                   |
+| `Ctrl`+click / `Cmd`+click a tab | Add that session to the grid.                            |
+
+While the grid is open, `Ctrl+Tab` and `Alt+[` / `Alt+]` cycle through the tiles, and the
+terminal shortcuts above act on the focused tile. **Remove Focused Tile** has no key by
+default. See [Tile Grid](Tile-Grid).
+
 ## Everything else
 
 | Shortcut       | Action                          |