feat(chat)!: remove per-message checkpoint marker; flatten chat-messa… #1197

Job	Run time
CI scope	5s
Library — lint / test / build	3m 44s
Website — lint / build	2m 4s
Cockpit — deploy smoke dry-run	1m 21s
Cockpit — representative capability smoke	1m 22s
Website — e2e	2m 51s
examples/chat — e2e	3m 39s
examples/chat — python smoke	1m 19s
Cockpit — build all examples	5m 18s
Cockpit — secret-gated integration	4s
Cockpit — e2e (cockpit-chat-interrupts-angular)	2m 9s
Cockpit — e2e (cockpit-langgraph-streaming-angular)	2m 2s
Cockpit — e2e (cockpit-chat-subagents-angular)	2m 10s
Cockpit — e2e (cockpit-chat-tool-calls-angular)	2m 12s
Cockpit — build / test	1m 38s
PostHog — dashboards-as-code drift check	6s
Cockpit — e2e	4s
Canonical demo → Vercel	3m 29s
Deploy → Vercel	19m 46s
Production smoke	6m 5s
	1h 1m 28s

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