feat(harness): manifest provider/model/thinking/name + session new options (BE-6/7)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

harness/tht/session/store.py

@@ -53,6 +53,8 @@ def _new_id(question: str, sessions_root: Path, stamp: str) -> str:
 def create_session(
     question: str, db: DatabaseConfig, sessions_root: Path,
     *, author: str | None = None, summary: str | None = None,
+    provider: str | None = None, model: str | None = None,
+    thinking: str | None = None, name: str | None = None,
 ) -> SessionManifest:
     now = datetime.now(UTC)
     # stamp con ora/min/sec: identifica univocamente sessioni dello stesso giorno
@@ -73,6 +75,7 @@ def create_session(
         database=db.database, schema=db.db_schema,
         author=who, summary=summary or _summarize(question),
         updated_at=now, updated_by=who, schema_version=schema_version,
+        provider=provider, model=model, thinking=thinking, name=name,
     )
     session_dir = sessions_root / session_id
     manifest.to_yaml(session_dir / MANIFEST)