special: keys go to a tile, and Esc only ever leaves

Inside the special workspace the agenda and the calendar could only be
reached with Alt-h/j/k/l, which a desktop that binds Alt to its own windows
never lets through, and the same keys meant two things: t on the agenda put
the whole workspace away, t elsewhere went to it. Three esc buttons, one per
tile, all closed everything.

Now b, t and C only ever go to their tile, from anywhere. Tab and Shift-Tab
walk the tiles, as they walk the spaces elsewhere; l past the board's last
list goes on into the agenda, h in the agenda back to the board, j past its
end into the calendar. S toggles the workspace, and q and Esc leave it from
whichever tile — after leaving fullscreen first. The tile buttons are gone;
each tile's head shows its key instead, lit on the one with focus, and the
bar has a special pill beside the spaces.

A document opened from the workspace — a day of the calendar, an entry of
the agenda, today's entry, a card's notes — comes back to the tile it was
opened from on q.

The board tile shows the board of the space being browsed, or else the last
one shown, so coming from the diary, which has none, no longer leaves it
empty. Card and list actions follow the board on screen, not the browsed
space.

docs/wiki/Guide.md

@@ -13,7 +13,7 @@ The keys are the desktop's. On a phone, every one of these has a button; see
 The first time you open the workspace each day, the **agenda** opens by itself
 when anything is late or due. Any other time, press `t`. It opens in the
 **special workspace**, beside the board and the calendar; `S` puts that up and
-away from anywhere, and `Alt-h`/`Alt-l` move between its tiles.
+away from anywhere, and `Tab` walks its tiles.
 
 ![The agenda](../images/agenda.png)
 
@@ -35,7 +35,7 @@ Walk it with `j` and `k`. On a card:
 - `H` and `L` move it to the list left or right on its board;
 - `Enter` goes to the card on its own board, in the tile beside.
 
-`Esc` or `t` puts the special workspace away. The bar keeps showing the `late` and `today`
+`Esc` leaves the special workspace. The bar keeps showing the `late` and `today`
 counts while either is above zero. More in [Boards and the agenda](Boards-and-Agenda.md).
 
 ## At work: spaces, documents and tiles