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.

web/src/lib/Rail.svelte

@@ -37,7 +37,7 @@
         { icon: 'board', label: 'Board', keys: ['b'], run: () => (workspace.specialFocus = 'board'), on: workspace.specialFocus === 'board' },
         { icon: 'agenda', label: 'Agenda — late, due, in hand', keys: ['t'], run: () => (workspace.specialFocus = 'agenda'), on: workspace.specialFocus === 'agenda' },
         { icon: 'calendar', label: 'Calendar', keys: ['C'], run: () => (workspace.specialFocus = 'calendar'), on: workspace.specialFocus === 'calendar' },
-        { icon: 'list', label: 'Back to the tree', keys: ['S', 'q'], run: () => workspace.closeSpecial() },
+        { icon: 'list', label: 'Back to the tree', keys: ['Esc', 'S'], run: () => workspace.closeSpecial() },
       ]
       if (workspace.specialFocus !== 'board') return [tiles, [cmd, help]]
       // The card verbs are doors too, so a phone — which has no H, L or