Set up dev environment + document Cursor Cloud caveats

[FluffyAIcode]

Summary

Sets up the OpenMontage development environment on the Cursor Cloud VM and documents non-obvious caveats for future agents in AGENTS.md.

The only code change is appending a ## Cursor Cloud specific instructions section to AGENTS.md. No application code was modified.

Environment setup performed

• Python deps: pip install -r requirements-dev.txt (core + pytest) and optional pip install piper-tts (free offline TTS)
• Remotion composer: npm install in remotion-composer/
• .env created from .env.example
• Registered an idempotent update script (deps refresh only)

Verification

• ✅ Preflight registry discovery — all three composition runtimes available (ffmpeg, remotion, hyperframes)
• ✅ Zero-key end-to-end render: python3 render_demo.py world-in-numbers produced a valid 1920×1080 H.264+AAC 23s MP4 via Remotion
• ✅ HyperFrames doctor passes (Node 22, ffmpeg, npx, hyperframes 0.7.36)
• ✅ Lint (py_compile) on the 3 existing lint-target files
• Contract tests: 257 passed, 6 skipped, 2 failed — both failures are pre-existing content/test drift unrelated to setup (documented in AGENTS.md)

Demo render (hello world)

world_in_numbers_demo.mp4
Rendered demo title card

Notable caveats (captured in AGENTS.md)

• No python executable on the VM — only python3; make targets that call python fail. Use python3 directly.
• make lint references a missing file (tools/composition_validator.py).
• HyperFrames headless Chrome renders may need more than the 64 MB /dev/shm available here.

_{To show artifacts inline, enable in settings.}