test(state): cover update_session_model overwrite + getattr-guard text path

Follow-up to LengR's #35181 salvage:
- gateway text-path uses getattr(self, '_session_db', None) to match the
  picker callback path (defensive for object.__new__() gateway test pattern).
- add SessionDB.update_session_model test asserting it overwrites the
  COALESCE-pinned model and survives subsequent token updates (#34850).

scripts/release.py

@@ -46,6 +46,7 @@ ACP_REGISTRY_MANIFEST = REPO_ROOT / "acp_registry" / "agent.json"
 # Auto-extracted from noreply emails + manual overrides
 AUTHOR_MAP = {
     "drpelagik@gmail.com": "SeaXen",
+    "lengr@users.noreply.github.com": "LengR",
     "metalclaudbot@gmail.com": "HashClawAI",
     "tonybear55665566@gmail.com": "TonyPepeBear",
     "kaspersniels@gmail.com": "nielskaspers",