Mobile Control has no session list and no way to start a session

[charlesrhoward]

Problem

Below 768 pixels the Control sidebar is hidden and the top bar has no New control. A user with an existing session sees only the transcript. They cannot switch sessions or start one.

Where

• components/control/session-list.tsx:266 and :309: both containers carry hidden ... md:flex.
• components/control/control-top-bar.tsx has no new-session or session-switch control.
• Reference pattern: components/top-bar.tsx:133-146 uses a left Sheet drawer for mobile navigation.

Fix

1. Add a menu button to the Control top bar, visible only below md, that opens SessionList inside a Sheet (same component as the desktop sidebar, no fork).
2. Make sure the New button inside the sheet goes through startNewSession from use-control-session-actions.ts, the same handler as every other entry point. Do not build a new target object.
3. Close the sheet on session select.

Exit criteria

• Playwright spec in tests/e2e/ at a 390 pixel viewport: open /control, open the drawer, click New, confirm the composer appears with the current project preselected.
• Manual on a phone or DevTools device mode: switch sessions and start a new one.
• pnpm lint, pnpm typecheck, pnpm test, targeted e2e pass.

Out of scope

GitHub issue #347 (mobile workspace shell). Two of its sub-items are real (components/mobile/workspace-shell.tsx:26,36 should use isPane(), and activeId is destructured and discarded at :75) but it is a different surface.

https://claude.ai/code/session_01SQ4nS96XYRztd5w9QkubPf