feat: non-destructive lock recovery for pushed branches (Closes #440)

Adds structured issue-branch ownership parsing, wires it into lock adoption
and gitea_lock_issue validation, documents the restart recovery workflow, and
adds regression tests for adoption, durable create_pr resolution, and open-PR
blocking without remote branch deletion.

Built on keyed persistent lock store and own-branch adoption (#443 / #442).

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

issue_lock_adoption.py

@@ -1,4 +1,4 @@
-"""Own-branch lock adoption / recovery for ``gitea_lock_issue`` (#442 / #443).
+"""Own-branch lock adoption / recovery for ``gitea_lock_issue`` (#440 / #442 / #443).
 
 When an issue's own already-pushed branch exists, lock reacquisition must be
 allowed (adoption) instead of being treated as #400 duplicate competing work.
@@ -14,6 +14,8 @@ this module additionally records whether they passed for proof purposes.
 
 from __future__ import annotations
 
+import issue_branch_ownership
+
 ADOPT = "adopt_existing_branch"
 BLOCK_COMPETING = "block_competing_branch"
 NO_MATCH = "no_matching_branch"
@@ -40,13 +42,12 @@ def assess_own_branch_adoption(
     existing_branches,
 ) -> dict:
     """Decide whether an existing matching branch is adoptable."""
-    marker = f"issue-{issue_number}"
     requested = (requested_branch or "").strip()
 
     matches: list[tuple[str, str | None]] = []
     for entry in existing_branches or []:
         name = _branch_name(entry).strip()
-        if marker in name:
+        if issue_branch_ownership.branch_belongs_to_issue(name, issue_number):
             matches.append((name, _branch_sha(entry)))
 
     competing = sorted({name for name, _ in matches if name != requested})