fix: durable author worktree resolution without control fallback (Closes #618)

Author mutation tools now resolve workspace via explicit worktree_path,
env bindings, or the active author issue lock — never silent fallback to
the control checkout/master. Missing configured bindings fail closed with
operator recovery; create_issue and create_issue_comment agree.

Recovered onto 0568f44 from preserved candidate cbf56ccd (AUTHOR_RECOVERY).
LLM_LOCK_ID=author-618-recovery-508eb3162d01-1784569919

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

tests/test_create_issue_workspace_guard.py

@@ -26,15 +26,23 @@ class TestCreateIssueWorkspaceGuard(unittest.TestCase):
         srv._preflight_whoami_called = True
         srv._preflight_capability_called = True
         srv._preflight_resolved_role = "author"
+        srv._preflight_resolved_task = "create_issue"
         srv._preflight_whoami_violation = False
         srv._preflight_capability_violation = False
         
         # Disable early return in verify_preflight_purity for testing
         self._orig_in_test = srv._preflight_in_test_mode
         srv._preflight_in_test_mode = lambda: False
+        # #618: isolate from ambient session issue locks
+        self._lock_patch = patch(
+            "gitea_mcp_server._session_author_lock_worktree", return_value=None
+        )
+        self._lock_patch.start()
 
     def tearDown(self):
         srv._preflight_in_test_mode = self._orig_in_test
+        srv._preflight_resolved_task = None
+        self._lock_patch.stop()
 
     @patch("gitea_mcp_server._auth", return_value=FAKE_AUTH)
     @patch("gitea_mcp_server._profile_permission_block", return_value=None)