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_branch_ownership.py

@@ -0,0 +1,28 @@
+"""Structured issue/branch ownership evidence (#440).
+
+Author branches must follow ``(fix|feat|docs|chore)/issue-<n>-<desc>``. Duplicate-work
+and lock-recovery gates use this parser instead of broad substring matching on
+``issue-<n>`` so unrelated branch names cannot false-positive.
+"""
+
+from __future__ import annotations
+
+import re
+
+ISSUE_BRANCH_RE = re.compile(
+    r"^(?P<prefix>fix|feat|docs|chore)/issue-(?P<num>\d+)(?:-|$)"
+)
+
+
+def parse_issue_branch(branch_name: str) -> int | None:
+    """Return the issue number encoded in a canonical author branch, else None."""
+    match = ISSUE_BRANCH_RE.match((branch_name or "").strip())
+    if not match:
+        return None
+    return int(match.group("num"))
+
+
+def branch_belongs_to_issue(branch_name: str, issue_number: int) -> bool:
+    """True when ``branch_name`` is a canonical branch for ``issue_number``."""
+    parsed = parse_issue_branch(branch_name)
+    return parsed is not None and parsed == issue_number