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]>

tests/test_mcp_server.py

@@ -3115,7 +3115,7 @@ class TestIssueLocking(unittest.TestCase):
     def test_lock_issue_mismatch_branch_fails(self):
         with self.assertRaises(ValueError) as ctx:
             gitea_lock_issue(issue_number=196, branch_name="feat/issue-195-mutations", remote="prgs")
-        self.assertIn("must contain locked issue pattern", str(ctx.exception))
+        self.assertIn("must match", str(ctx.exception))
 
     @patch(
         "mcp_server.issue_lock_worktree.read_worktree_git_state",