docs(tiles): moving tiles, by the header and by Ctrl+Shift+Arrows

The wiki's Tile Grid page gets a "Moving tiles" section and the move
chords in its keys table (with what they leave to a text field and
take from a terminal editor inside a tile); Keyboard Shortcuts lists
the chords and the header drag. The spec records moving as an owner
request in its as-built list, with the reasoning behind the default
keys. The invariants and CLAUDE.md say every move goes through
_reorderTiles (no remount, reconnect or reload; only a tile whose cell
size changed fits) and that the header drag carries its own type and
is not draggedTabId.

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

docs/wiki/Keyboard-Shortcuts.md

@@ -45,6 +45,8 @@ Anything you copy is cleaned on the way to the clipboard: each line loses the pa
 | --------------------------- | ------------------------------------------------------------ |
 | `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.            |
+| `Ctrl+Shift+Arrows`         | Move the focused tile: it trades places with that neighbour.  |
+| 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.                  |