test(audit): Phase 10 - 7 integration tests against synthetic src/

Updated synthetic ai_client.py + aggregate.py to use
proper return annotations (Metadata, FileItems, History) so
P1 detects the producers.

7 integration tests:
1. synthetic src/ produces 10 real + 3 candidate profiles
2. Metadata has >=1 producer (after fixing fixture annotations)
3. Metadata memory_dim is 'discussion' (canonical)
4. FileItems memory_dim is 'curation' (canonical)
5. History memory_dim is 'discussion' (canonical)
6. Missing audit_inputs tolerated
7. render_rollups produces 4 non-empty rollup files

131 tests total passing.

tests/fixtures/synthetic_src/aggregate.py

@@ -1,15 +1,15 @@
 """Synthetic aggregate module for the v2 audit integration tests."""
 from __future__ import annotations
-from typing import Any
+from typing import Any, List
 
-FileItems = list[dict[str, Any]]
+FileItems = List[dict[str, Any]]
 
-def build_file_items() -> list[dict[str, Any]]:
+def build_file_items() -> FileItems:
  data: FileItems = [{"path": "a.py", "view_mode": "full"}, {"path": "b.py", "view_mode": "summary"}]
  return data
 
-def format_paths(items: FileItems) -> list[str]:
- out: list[str] = []
+def format_paths(items: FileItems) -> List[str]:
+ out: List[str] = []
  for item in items:
   path = item["path"]
   view_mode = item["view_mode"]

tests/fixtures/synthetic_src/ai_client.py

@@ -1,15 +1,15 @@
 """Synthetic AI client for the v2 audit integration tests."""
 from __future__ import annotations
-from typing import Any
+from typing import Any, List
 
 Metadata = dict[str, Any]
-History = list[dict[str, Any]]
+History = List[dict[str, Any]]
 
-def send_result() -> dict[str, Any]:
+def send_result() -> Metadata:
  data: Metadata = {"role": "user", "content": "hello"}
  return data
 
-def append_history() -> list[dict[str, Any]]:
+def append_history() -> History:
  data: History = []
  return data