fix: add external_id to test stub classes after merge

The merge from main introduced external_id to project objects.
Update stub classes in tests to include this attribute.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: phernandez

tests/mcp/test_tool_recent_activity.py

@@ -267,6 +267,7 @@ async def fake_call_get(client, url, params=None):
 
     class P:
         id = 1
+        external_id = "test-external-id"
         name = "p"
         path = "/tmp/p"
 

tests/mcp/test_tool_search.py

@@ -297,6 +297,7 @@ class StubProject:
             project_url = "http://test"
             name = "test-project"
             id = 1
+            external_id = "test-external-id"
 
         async def fake_get_active_project(*args, **kwargs):
             return StubProject()
@@ -322,6 +323,7 @@ class StubProject:
             project_url = "http://test"
             name = "test-project"
             id = 1
+            external_id = "test-external-id"
 
         async def fake_get_active_project(*args, **kwargs):
             return StubProject()