fix(tui): keep the way out on the bar, and make Alt+1..9 actually switch

Four faults, all reported at once, and three of them were mine from the last
two commits.

THE HINT VANISHED. Two independent causes. First, a leaked F1 binding: an
attach whose TUI was killed leaves `F1 -> detach-client` in tmux's root table,
and the claim treated "already bound" as someone else's key, so every later
attach fell back to advertising the tmux chord — the bar stopped saying F1
while F1 still worked. A key already bound to `detach-client` now counts as
ours. Second, width: tmux truncates a status line that overflows and drops the
RIGHT-aligned segment, which is the hint. The strip now gets a budget measured
from the terminal's width minus the hint, and it drops tabs from the far end
until it fits. ⚠️ Measured on VISIBLE columns, not format bytes: `#[reverse]`
costs zero columns, and counting it made a strip that "fitted" still truncate
the hint at 80, 100, 120 and 176 columns on a real terminal.

ALT+N DID NOT SWITCH. On the dashboard, a bare digit meant jump AND ATTACH, and
a terminal sends Alt+N as ESC then N: when those land in separate reads —
routine over SSH — the chord decodes as Escape plus a bare digit, so "switch to
tab 2" threw the user into tab 2's pane. A digit now SELECTS, matching what
Alt+N means in the web UI; Enter is how you go in. Inside a pane the keys never
reached the TUI at all, since tmux owns the terminal, so the attach now binds
Alt+1..9 in tmux's root table to `switch-client` — the strip is usable rather
than decorative. ⚠️ The bar is applied to every session the strip can reach,
each highlighting its own tab: with it on the attached session only, switching
landed the user in a pane with no strip and no way out on screen.

⚠️ The leaked-state sweep was missing `status-position`, so it removed the
marker and left the position behind — and with no marker the leftover no longer
matched, making it permanently unsweepable. Found by diffing every session's
options after a detach.

test/tui/tui-render.test.ts

@@ -158,7 +158,7 @@ describe('renderFrame structure', () => {
       '                                    │',
       '                                    │',
       '                                    │',
-      ' ↑↓ select · ↵ attach · 1-9 jump · y/n answer · p prompt · n new · x kill · / search · g digest · ?',
+      ' ↑↓ select · ↵ attach · 1-9 switch · y/n answer · p prompt · n new · x kill · / search · g digest ·',
     ]);
   });
 
@@ -183,7 +183,7 @@ describe('renderFrame structure', () => {
       '',
       '',
       '',
-      ' ↑↓ select · ↵ attach · 1-9 jump · y/n answe',
+      ' ↑↓ select · ↵ attach · 1-9 switch · y/n ans',
     ]);
   });