fix: inject duplicate-work context fetcher for testable lock/create_pr paths (#400)

Expose issue_duplicate_context_fetcher on the MCP server so lock_issue,
commit_files, and create_pr duplicate rechecks avoid live Gitea calls in
unit tests. Update affected test suites to patch the fetcher without
weakening duplicate-work gate assertions.

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

tests/test_commit_files_capability.py

@@ -76,7 +76,14 @@ class CommitFilesCapabilityBase(unittest.TestCase):
         with open(self.config_path, "w", encoding="utf-8") as fh:
             fh.write(json.dumps(CONFIG))
 
+        self._dup_fetcher_patcher = patch(
+            "mcp_server.issue_duplicate_context_fetcher",
+            return_value=([], [], {"status": "not_claimed"}),
+        )
+        self._dup_fetcher_patcher.start()
+
     def tearDown(self):
+        self._dup_fetcher_patcher.stop()
         self._remotes.stop()
         mcp_server._IDENTITY_CACHE.clear()
         mcp_server._preflight_whoami_called, mcp_server._preflight_capability_called = (