feat(chat): decouple primitives from LangGraph via runtime-neutral ChatAgent contract #406

Job	Run time
Cockpit — secret-gated integration	1m 37s
Cockpit — build all examples	5m 4s
Website — lint / build	1m 54s
Website — e2e	2m 34s
Cockpit — e2e	2m 11s
Cockpit — build / test	2m 2s
Cockpit — deploy smoke dry-run	1m 26s
Library — lint / test / build	1m 38s
Cockpit — representative capability smoke	1m 30s
Chat Agent — smoke	1m 47s
Deploy → Vercel	0s
Production smoke	0s
	21m 43s

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