tmux that actually persists, and a running-shells panel

The Tmux panel typed bare `tmux`, which starts a NEW session every time — so the panel
forgot your windows whenever the shell behind it went away, including on a
`pm2 restart officer-pty`. It now runs `new-session -A -s <name>`, which attaches if the
session exists and creates it otherwise, named per panel from panelId (stable in the saved
layout). The tmux server outlives the pty, so this survives what a pty session cannot.

CommandTerminalWrapper had the same unmount bug TerminalWrapper did — it deleted the panel
-> session mapping on unmount, so every layout change abandoned the shell AND re-ran the
command from scratch. Kept across unmounts now, same as the plain terminal.

Two things the seeded .tmux.conf needs that were missing:

- COLORTERM=truecolor in the pty env. TERM only advertises 256 colours, and COLORTERM is
  what programs check before emitting 24-bit — so we were throwing away colour depth for
  tmux, neovim, bat, delta and any modern TUI. xterm.js renders it fine.
- macOptionIsMeta. On macOS Option is a compose key, so Alt bindings never reach the shell
  — silently breaking the M-arrow and M-hjkl pane switching the config leans on. No effect
  on other platforms. Also rightClickSelectsWord, so right-click stops opening the browser
  menu over the terminal.

Adds a Running Shells panel: every shell the sidecar holds, with the title it set for
itself (usually the running command), pid, size, idle and uptime, and a kill button.
That is the other half of keeping session mappings across unmounts — the leak stops being
invisible, and stops needing curl to find.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/servers/sidecar/pty/index.mjs

@@ -133,7 +133,10 @@ async function handleCommand(msg) {
           cols,
           rows,
           cwd,
-          env: { ...process.env, TERM: 'xterm-256color' },
+          // COLORTERM is how programs decide they may emit 24-bit colour — TERM only advertises 256.
+          // xterm.js renders truecolor fine, so without this we were throwing away colour depth for
+          // anything that checks (tmux with `*:RGB`, neovim, bat, delta, modern TUIs).
+          env: { ...process.env, TERM: 'xterm-256color', COLORTERM: 'truecolor' },
         });
       } catch (err) {
         const message = err instanceof Error ? err.message : 'Failed to start terminal';