docs(tiles): the count menu, the open/close animation and the paced open

- docs/tile-grid-plan.md: owner decision 10 (right-click Tiles is a
  2 / 4 / 6 count menu, default 6, remembered per device; the session
  picker is gone; decision 8's "picker on right-click" and "exactly the
  stored set" superseded) with the owner's answers on the details; three
  as-built bullets (the count menu, the animation, painting first); the
  Tiles-button bullet rewritten for the count; the entry points, the
  capacity note, the multi-user row and the Escape invariant follow.
- docs/architecture-invariants.md: the Opening paragraph rewritten (the
  count, the stored grid in its cells, the menu owning its Escape, the
  paced connect and focusOnConnect, the motion rules); the z-index list
  names the count menu and the closing grid's still copy.
- CLAUDE.md: the tile grid paragraph and the z-index line.
- Wiki: Tile Grid (the click, the count menu, the animation, reduced
  motion) and Keyboard Shortcuts (right-click Tiles).

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

docs/wiki/Keyboard-Shortcuts.md

@@ -49,7 +49,7 @@ Anything you copy is cleaned on the way to the clipboard: each line loses the pa
 | Drag a tile's header        | Move the tile: onto another tile they swap, onto an empty slot it moves there. |
 | `Alt+Shift+Enter`           | Zoom the focused tile, or restore the grid.                   |
 | `Ctrl`+click / `Cmd`+click a tab | Add that session to the grid.                            |
-| Right-click the Tiles button | Choose which sessions to show as tiles.                  |
+| Right-click the Tiles button | Choose how many tiles: 2, 4 or 6 (remembered).           |
 
 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