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]>

issue_branch_ownership.py

@@ -0,0 +1,31 @@
+"""Structured issue/branch ownership evidence (#440).
+
+Author branches must follow ``(fix|feat|docs|chore)/issue-<n>-<desc>``. Duplicate-work
+and recovery gates use this parser instead of broad substring checks like
+``issue-420`` inside unrelated names (for example ``issue-4200``).
+"""
+
+from __future__ import annotations
+
+import re
+
+IMPLEMENTATION_BRANCH_RE = re.compile(
+    r"^(?:fix|feat|docs|chore)/issue-(\d+)(?:-.+)?$"
+)
+
+
+def parse_tracked_issue_number(branch_name: str) -> int | None:
+    """Return the issue number encoded in a canonical author branch name."""
+    text = (branch_name or "").strip()
+    if not text:
+        return None
+    match = IMPLEMENTATION_BRANCH_RE.match(text)
+    if not match:
+        return None
+    return int(match.group(1))
+
+
+def branch_tracks_issue(branch_name: str, issue_number: int) -> bool:
+    """True when ``branch_name`` structurally belongs to ``issue_number``."""
+    parsed = parse_tracked_issue_number(branch_name)
+    return parsed == issue_number if parsed is not None else False