feat: isolate project agent threads in worktrees

[oscarlehuu]

Summary

• give every non-DM top-level task/thread its own ACP queue, session, control, and typing identity while preserving the real NIP-29 channel for relay/UI operations
• create one deterministic Git worktree per Project thread and reuse it across explicit agent handoffs
• keep the normal Slack-style composer: the first ordered agent runs, later named agents remain reference-only until explicitly handed off in the thread
• preserve exact conversationId and turnId for cancel/model-switch controls so simultaneous same-channel turns can be controlled independently

Safety

• freeze workspace authority to the trusted owner-authored thread root, including after Project relinks
• fail closed when workspace metadata, root lookup, repository validation, or provisioning fails; never fall back to the shared source checkout
• deterministic branch/worktree identity derives from the immutable root event ID, not raw prompt text
• channel-only control fallback refuses ambiguous multi-thread routing

Verification

• full just ci passed
• buzz-acp: 651 unit tests + 9 lifecycle tests passed
• desktop: 3873 passed, 1 gated live-relay test skipped, 0 failed
• focused browser E2E: 62 boot, composer, mention, messaging, and thread-anchor scenarios passed
• reviewer and independent tester cleared Project-relink, same-channel concurrency, exact cancel, and truthful model-switch edge cases
• local macOS arm64 NuncioCrew Local.app built, ad-hoc signed, and passed strict codesign verification

Related

• PR fix(desktop): arch-scope managed node-tools and self-repair adapters #5 was merged first and this branch was rebased onto its merge commit.