fix(agent): raise tool rounds and ease calendar creates

Local models were burning the 8-round budget on simple event adds.
Raise the limit, resolve calendars by name/default, and inject the
household clock so relative dates work.

.env.example

@@ -55,3 +55,5 @@ LLM_PROVIDER=openai
 LLM_BASE_URL=
 LLM_API_KEY=
 LLM_MODEL=llama3.2
+# IANA timezone for assistant relative dates ("Thursday at 2"). Falls back to TZ, then America/Chicago.
+HOUSEHOLD_TIMEZONE=America/Chicago