feat: group threads and shared resources by worktree

[jakeleventhal]

What Changed

Demo video and explanation/rationale

Group conversations by environment, project, and checkout across the web/desktop sidebar and mobile Home/navigation lists. Project, machine, branch, PR, and terminal information appears once per group, while each thread retains its title, provider, and status.

• Reorder whole worktree cards on web. Apply pin/unpin, settle/unsettle, and snooze/unsnooze to the worktree from either its header or a member thread’s menu.
• Share checkout resources across sibling threads: terminals across clients, plus preview tabs, files, diffs, and workspace panels on web/desktop. Keep those resources alive when a sibling is removed and clean up terminal resources after the final thread is removed.
• Make Cmd+T inherit the current checkout and branch, including drafts and local checkouts without branch metadata, regardless of the default new-worktree setting.

Why

Conversations in the same checkout currently repeat workspace information and can lose access to shared resources when switching threads. Grouping by checkout makes ownership and lifecycle actions consistent while preserving separate conversation histories. Environment-scoped identity keeps identical checkout paths on different machines separate.

Validation

Validation recorded during implementation:

• 109 focused sidebar/mobile list tests passed for the grouping and presentation changes.
• 38 focused thread-creation tests passed after the Cmd+T fix.
• Web and mobile typechecks passed for the UI changes; web typecheck passed again after the Cmd+T fix.
• Web layout was checked in the browser. The preceding UI revision was rebuilt and launched on desktop and a physical iPhone; native mobile visual verification is still pending.

UI Changes

Draft pending hosted before/after screenshots and a short video of whole-worktree drag/reorder. No visual evidence is attached yet.

Remaining before review

• Attach visual evidence and verify the native mobile layout.
• Update the existing worktree guide’s lifecycle and shortcut descriptions to match the final behavior.

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes
• I included a video for animation/interaction changes

Implemented with GPT-6 in Codex.

[jakeleventhal]

bruh

[TaylorMerritt]

Would love to see this come back in some form. I often have multiple threads for the same worktree, and having them grouped together would make the sidebar way easier to manage.