feat: run devloop in isolated worktrees

[satyaborg]

Summary

• Run Devloop in an isolated sibling git worktree by default so agent edits do not touch the caller's checkout.
• Add --in-place as the opt-out path for the old current-worktree behavior.
• Surface worktree/source metadata in tracks, reports, CLI/TUI output, docs, and tests.

Test plan

• bun run typecheck
• bun test