terminals: re-attach on reopen, and make orphaned shells findable

Closing a terminal panel abandoned its shell. TerminalWrapper deleted the panel -> session
mapping on *unmount*, so any layout or route change generated a fresh uuid on the way back
and left the old shell running: alive, unreachable, and never killed, because nothing has
ever sent pty:close. The mapping now outlives the mount, so reopening a panel re-attaches
to the shell you left — which is also what finally makes the sidecar's replay buffer worth
having. It is persisted dashboard state, so this survives a reload too.

That trades an invisible leak for a visible one: a panel deleted for good still leaves its
shell behind. So `pty:list` now enumerates live sessions, and GET /api/terminal/sessions +
DELETE /api/terminal/sessions/:id expose them. pty:close finally has a sender.

Each session carries createdAt, lastActivityAt, pid, and the title the shell sets for
itself via OSC 0/2 — usually the running command, which is what turns "some uuid" into
"the one running claude" when you are deciding what to kill.

Killing on unmount is still not an option: it needs the panel system to distinguish a real
close from an incidental remount, which it cannot currently do.

Also raises the sidecar replay buffer from 50KB to 512KB — 50KB was about one long agent
turn, so reconnecting mid-task showed you the tail and nothing before it — and cuts the
buffer on a line boundary rather than a byte offset. A blind slice can land inside an
escape sequence, and the replay then opens with the tail of a colour or cursor-move code,
which xterm renders as garbage or applies as a real instruction.

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

src/servers/hono.ts

@@ -27,6 +27,7 @@ import { transmissionRouter } from './api/transmission/router';
 import { invoiceshelfRouter } from './api/invoiceshelf/router';
 import { walletRouter } from './api/wallet/router';
 import { vpnRouter } from './api/vpn/router';
+import { terminalRouter } from './api/terminal/router';
 import { systemMonitorRouter } from './api/system-monitor/system-monitor';
 import { activityRouter } from './api/activity/router';
 import './api/music/sidecar-server'; // side-effect: capture the officer-music audio server port
@@ -113,6 +114,7 @@ protectedRouter.route('/task-logs', taskLogsRouter);
 protectedRouter.route('/file-browser', fileBrowserRouter);
 protectedRouter.route('/music', musicRouter);
 protectedRouter.route('/slskd', slskdRouter);
+protectedRouter.route('/terminal', terminalRouter);
 protectedRouter.route('/headscale', headscaleRouter);
 protectedRouter.route('/transmission', transmissionRouter);
 protectedRouter.route('/invoiceshelf', invoiceshelfRouter);