feat: non-destructive branch recovery after lost issue locks (Closes #440)

Implements the #420 recovery umbrella: keyed persistent issue locks with
own-branch adoption, structured branch ownership parsing, create_pr lock
resolution after MCP restart, and workflow docs forbidding destructive
branch deletion as the default recovery path.

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

gitea_mcp_server.py

@@ -537,6 +537,7 @@ import role_namespace_gate  # noqa: E402
 import task_capability_map  # noqa: E402
 import review_proofs  # noqa: E402
 import agent_temp_artifacts
+import issue_branch_ownership  # noqa: E402
 import issue_lock_worktree  # noqa: E402
 import issue_lock_store  # noqa: E402
 import issue_lock_adoption  # noqa: E402
@@ -1226,7 +1227,7 @@ def gitea_lock_issue(
         pr_title = pr.get("title", "")
         pr_body = pr.get("body", "")
 
-        if expected_pattern in pr_head:
+        if issue_branch_ownership.branch_tracks_issue(pr_head, issue_number):
             raise ValueError(
                 f"Issue #{issue_number} is already tied to an open PR (PR #{pr.get('number')}, branch '{pr_head}') (fail closed)"
             )