feat: Phase 7b - LockGuardedToolExecutor for write tool lock integration

[roomote-v0]

This PR attempts to address Issue #12330 by implementing Phase 7b -- integrating the FileLockManager (Phase 7a) into the tool execution layer.

What it includes

• LockGuardedToolExecutor class that wraps write tool execution with advisory file lock acquisition/release
• extractWriteTargetPaths() utility to extract target file paths from each write tool's parameters (write_to_file, apply_diff, apply_patch, edit_file, search_replace, search_and_replace)
• All-or-nothing lock semantics: if any file in a multi-file operation (e.g., apply_patch) cannot be locked, all acquired locks are rolled back
• Deadlock prevention: lock acquisition order is sorted by path
• Conflict error formatting: formatLockConflictError() produces LLM-friendly messages explaining why a write was blocked
• 26 unit tests covering path extraction, lock acquisition, conflict detection, rollback, and error formatting

Stacked branching

main -> Phase 1 -> Phase 2+3 -> Phase 4+5+6 -> Phase 7a -> Phase 7b (this PR)

Design decisions

• Non-invasive: The executor is a standalone class that the tool execution layer calls before/after write tools. No modifications to existing tool classes.
• Advisory locking: Consistent with Phase 7a's design -- locks are checked programmatically, not at the OS level.
• Re-entrant: Same task can re-acquire locks it already holds (useful for retry scenarios).

Next steps

Integration into the actual tool dispatch flow (wiring LockGuardedToolExecutor into the tool runner that calls BaseTool.execute()).

Feedback and guidance are welcome.

Interactively review PR in Roo Code Cloud

[roomote-v0]

Closing in favor of consolidated PR #12356 which merges all Phase 7 work into a single PR as requested.