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.

README.md

@@ -137,7 +137,7 @@ it; in the document pane it is that document. In the browse pane:
 | `R` | rename what is highlighted — a document, a folder or a file — starting from its name (`:name!` renames the space) |
 | `m` / `p` | pick nodes up — `m` again puts one back, `M` takes the whole folder — then drop them all into the folder you walk to |
 | `Ctrl`/`Shift`-click | pick a row up / every row from the cursor to it; drag picked-up rows onto a folder, a crumb or a space |
-| `S` | the special workspace: the board, the agenda and the calendar side by side; `Alt-h`/`j`/`k`/`l` move between them, `f` gives one the screen |
+| `S` | the special workspace: the board, the agenda and the calendar side by side; `Tab` or `Alt-h`/`j`/`k`/`l` move between them, `f` gives one the screen, `Esc` leaves |
 | `b` | the board of this space, in the special workspace; a digit there shows another space's |
 | `t` | the agenda: what is late, due this week, or in hand, on every board, in the special workspace |
 | `T` | today's diary entry, started if there is none |
@@ -244,7 +244,7 @@ start as `sftp_host_key` in the data directory.
 
 `b`, the board door on the rail, or `:board` swaps the tree for the special
 workspace — the board of the space being browsed, with the agenda and the
-calendar beside it — and swaps it back. Every space has one except the
+calendar beside it — and `Esc` swaps it back. Every space has one except the
 diary — a journal has no backlog — and `:set board` / `:set noboard` changes
 that for the space you are in (the dimmed board door on the rail does the
 same). A new board starts with `backlog`, `doing` and `done`, and the columns mean