session-memory Phase 0: normalized schema (T01) + Claude adapter (T02)

- session_memory/core/schema.py: Session/SessionEvent/Cost dataclasses,
  flavor-prefixed uids, watermarks, kind/outcome validation (T01)
- session_memory/adapters/claude.py: JSONL -> Normalized bundle, turn DAG
  via uuid/parentUuid, kind mapping, cost from message.usage (T02)
- tests: schema round-trip + adapter (synthetic + real local session)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -174,3 +174,9 @@ cython_debug/
 # PyPI configuration file
 .pypirc
 
+
+# session-memory local store
+session_memory/.store/
+__pycache__/
+*.pyc
+.pytest_cache/