test(quality): fix fake tests and add missing coverage

P0 fixes:
- telemetry: rewrite fake tests with real behavior verification (25 tests)
- config: delete copied-source tests, use proper imports (2 deleted)
- persistence: fix try-except pass to verify specific errors

P1 fixes:
- pipeline: add real FixedWindowAlgo tests instead of mocks (12 tests)
- provider: add SessionManager and ToolManager tests (25 tests)
- storage: add S3StorageProvider tests with moto mock (16 tests)
- plugin: add handler action tests for setting inheritance (15 tests)
- rag: add file storage and ZIP processing tests (21 tests)
- vector: add VDB filter conversion tests (30 tests)

P2 fixes:
- pipeline/msgtrun: strengthen assertions for exact message count
- api: add response structure validation in integration tests

New test files:
- provider/test_session_manager.py
- provider/test_tool_manager.py
- storage/test_s3storage.py
- plugin/test_handler_actions.py
- rag/test_file_storage.py
- vector/test_vdb_filter_conversion.py

Source code bugs documented:
- provider: TokenManager.next_token() ZeroDivisionError
- telemetry: send_tasks class variable shared state
- command: empty command IndexError, unused parameters
- utils: funcschema KeyError
- entity: vector.py independent declarative_base

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

pyproject.toml

@@ -122,6 +122,7 @@ package-data = { "langbot" = ["templates/**", "pkg/provider/modelmgr/requesters/
 
 [dependency-groups]
 dev = [
+    "moto>=5.2.1",
     "pre-commit>=4.2.0",
     "pytest>=9.0.3",
     "pytest-asyncio>=1.0.0",