feat: add generic playbook, worker, and teach runtime foundations

[s-JoL]

Summary

Add the generic Understudy runtime foundation on top of main without bringing in demo4-specific skills or assets.

This PR focuses on the reusable agent capabilities behind demos 1-3:

• workspace artifacts and teach drafts
• playbook and worker runtimes
• grounded GUI typing and browser routing
• configurable GUI grounding models
• browser extension relay bootstrap and fallback hardening
• generic docs/examples refresh
• session-backed teach-analysis hardening for real /teach stop flows

Changes

• add workspace artifact storage, teach draft plumbing, and playbook run support across core/gateway
• add playbook and worker runtimes so executable artifacts can be run directly by the agent
• add grounded GUI typing, browser routing, relay bootstrap, and CLI support for configurable grounding models
• harden generic execution and GUI runtime behavior, including empty-final recovery and watchdog timeout handling
• make session-backed video teach analysis bounded and more reliable by using no-tool internal sessions, explicit timeouts, and smaller default evidence packs
• refresh the generic docs and example walkthroughs for demo1, demo2, and demo3
• remove demo4-specific references from this branch so it stays aligned with the mainline generic product surface

Test evidence

pnpm build
# pass

pnpm typecheck
# pass

pnpm vitest run packages/tools/src/__tests__/video-teach-analyzer.test.ts
# pass (11 tests)

pnpm test:e2e:playbook:synthetic
# pass

Real end-to-end validation:

• main demo1 passed and produced /Users/songliang/Downloads/main-demo1-e2e.pptx
• this branch demo1 passed and produced /Users/songliang/Downloads/generic-demo1-e2e.pptx
• main demo2 passed and produced /Users/songliang/Desktop/main-demo2-meeting-notes.txt
• this branch demo2 passed and produced /Users/songliang/Desktop/generic-demo2-meeting-notes.txt
• this branch demo3 passed through the normal /teach start -> demonstrate -> /teach stop flow and produced teach draft 4d4272dc6ad7

Checklist

• pnpm lint passes
• pnpm typecheck passes
• pnpm test passes
• Tests added for new behavior
• Docs updated if behavior or APIs changed

[chatgpt-codex-connector]

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[s-JoL]

@claude