[opencode-agent]

Summary

Stacked on #55665. This updates the "Choose worktree" menu shown when a session's directory is missing so it uses the shared WorkspaceSubmenu.

• The menu keeps "New worktree" at the top level. Existing worktrees now sit under a "Worktree" submenu, the same layout as the new-session picker.
• With 10 or more worktrees, the submenu has a search field and a scrolling list. The old menu was a flat list with no search, limited to max-h-80.
• disabled={move.isPending} replaces the per-item disabled flags. There is no "View all" here.
• Worktree rows now use outline-worktree instead of workspace-isolated, which matches the picker. Rows no longer have a full-path title tooltip, because the shared submenu shows only the filename.
• The "Loading" row stays at the top level while the first worktree list is still empty.

Before / After

Desktop web, 1280×640, a session with a missing directory and 14 other worktrees. Screenshots were shared in the review thread.

Testing

• packages/app: bun typecheck
• packages/app: e2e/regression/session-location-sync.spec.ts (9 passed). The recovery test now opens the "Worktree" submenu before picking a worktree.

Requested by: @Brendonovich (Brendan via Slack)

[opencode-agent]

Folded into #55665.