fix: address review findings — backward compat, ACP safety, result timing, security

- Fix 1: tasks_md_sync only sets MACP fields when columns exist in table headers
- Fix 2: ACP dispatch now escalates instead of falsely completing
- Fix 3: Removed premature collect_result() from dispatch_task()
- Fix 4: Yolo brief staged via temp file (0600) instead of process args
- Fix 5: cleanup_worktree validates path against configured worktree base

tools/orchestrator-matrix/README.md

@@ -99,6 +99,8 @@ Controller behavior remains backward compatible:
 
 - Tasks without `dispatch` continue through the legacy shell execution path.
 - Tasks with `dispatch` use the MACP dispatcher and can emit `task.gated` and `task.escalated`.
+- `acp` dispatch is fail-safe in Phase 1: it escalates with `ACP dispatch requires OpenClaw integration (Phase 2)` instead of reporting success.
+- `yolo` dispatch stages the brief in a temporary file so the brief body does not appear in process arguments.
 
 Manual queue operations are exposed through: