chore: remove unused demo projects #471

Job	Run time
Library — lint / test / build	2m 15s
Website — e2e	2m 5s
Website — lint / build	1m 44s
Cockpit — secret-gated integration	1m 4s
Cockpit — build all examples	4m 49s
Cockpit — build / test	1m 38s
Cockpit — e2e	1m 47s
Chat Agent — smoke	1m 6s
Cockpit — representative capability smoke	1m 10s
Cockpit — deploy smoke dry-run	1m 8s
Deploy → Vercel	-1s
Production smoke	0s
	18m 45s

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