feat: harden issue lock store against concurrent session clobbering (Closes #438)

Replace read-modify-write on the global /tmp/gitea_issue_lock.json pointer with
atomic per-issue locks under GITEA_ISSUE_LOCK_DIR using flock serialization,
PID/session metadata, fail-closed stale recovery, and pre-mutation freshness
re-checks in gitea_create_pr. Queue inventory now surfaces live_issue_locks.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

merged_cleanup_reconcile.py

@@ -13,6 +13,7 @@ import subprocess
 from typing import Any
 
 from reviewer_worktree import parse_dirty_tracked_files
+import issue_lock_store
 
 PROTECTED_BRANCHES = frozenset({"master", "main", "dev"})
 ISSUE_LOCK_FILE = os.environ.get("GITEA_ISSUE_LOCK_FILE", "/tmp/gitea_issue_lock.json")
@@ -49,6 +50,10 @@ def read_issue_lock(path: str | None = None) -> dict[str, Any] | None:
 
 
 def has_active_issue_lock(branch: str, lock_path: str | None = None) -> bool:
+    lock = issue_lock_store.resolve_lock_for_branch(branch)
+    if lock and (lock.get("branch_name") or "").strip() == (branch or "").strip():
+        freshness = issue_lock_store.assess_lock_freshness(lock)
+        return freshness["live"]
     lock = read_issue_lock(lock_path)
     if not lock:
         return False