test(audit): Phase 10 fixtures - synthetic src/ + 6 audit_inputs JSONs

synthetic_src/:
- type_aliases.py (3 TypeAliases: Metadata, FileItems, History)
- ai_client.py (producer + consumer of Metadata + History)
- aggregate.py (producer + consumer of FileItems)
- gui_2.py (hot-path consumer of FileItems)
- cleanup.py (cold-path consumer of Metadata)
- overrides.toml (frequency override for cleanup.do_nothing)

audit_inputs/ (6 JSON files):
- audit_weak_types.json (4 findings in Metadata + FileItems functions)
- audit_exception_handling.json (2 BOUNDARY_SDK findings)
- audit_optional_in_3_files.json (0 findings)
- audit_no_models_config_io.json (0 findings)
- audit_main_thread_imports.json (0 findings)
- type_registry.json (3 aggregates' field sets)

tests/fixtures/audit_inputs/audit_exception_handling.json

@@ -0,0 +1,6 @@
+{
+ "findings": [
+  {"file": "tests/fixtures/synthetic_src/ai_client.py", "line": 14, "category": "BOUNDARY_SDK", "function": "send_result", "class": null, "body_summary": "try/except + Result conversion"},
+  {"file": "tests/fixtures/synthetic_src/aggregate.py", "line": 11, "category": "BOUNDARY_SDK", "function": "build_file_items", "class": null, "body_summary": "try/except + Result conversion"}
+ ]
+}