[bugfix]: dreamverse modal bypasses ENTRYPOINT — set ffmpeg env + key check

[alexzms]

Summary

Modal's @modal.web_server decorator invokes serve() directly (Popen the dreamverse-server) and bypasses the image's ENTRYPOINT (apps/dreamverse/docker/docker_entrypoint.sh). The bypassed entrypoint normally does two things that silently no-op on Modal:

1. :?-validates CEREBRAS_API_KEY and GROQ_API_KEY (fails the container fast if either is missing from the mounted secret).
2. Sources ffmpeg-env.sh, which exports FASTVIDEO_FFMPEG_BIN=/opt/ffmpeg-native/bin/ffmpeg.

Symptoms observed

Deploying the post-#1394 UI image (dreamverse-ui-cuda12.9.1-sha-2c13793) on Modal:

• No ffmpeg, video silently broken. /opt/ffmpeg-native/bin is not on the container PATH (apps/dreamverse/docker/Dockerfile:24). With FASTVIDEO_FFMPEG_BIN unset, av_streaming.py:28's shutil.which("ffmpeg") returns None and av_fmp4 muxing has no encoder.
• Missing keys surface at first request, not boot. A dreamverse-api-keys secret with placeholder values lets the container come up fine; prompt rewriting then fails on the first user request instead of at boot.

Fix

Both changes in apps/dreamverse/scripts/modal/modal_app.py:

1. Set FASTVIDEO_FFMPEG_BIN=/opt/ffmpeg-native/bin/ffmpeg and FASTVIDEO_VIDEO_CODEC=libx264 in image.env so av_streaming finds the native ffmpeg the Dockerfile builds.
2. Add a fail-fast guard in serve() that checks the required secret entries before launching the server, mirroring the entrypoint's :? behavior.

A comment block above the env dict documents why these are needed (entrypoint bypass), so the next reader doesn't lose the context.

Test evidence

• pre-commit run --files apps/dreamverse/scripts/modal/modal_app.py and python -c "import ast; ast.parse(open(...))" pass.
• The ffmpeg gap was empirically discovered while bringing up the dreamverse Modal deploy with the post-[bugfix] Fix Dreamverse Modal compile warmup latency #1394 image; setting FASTVIDEO_FFMPEG_BIN in image.env was the workaround that made av_streaming's shutil.which resolve to the right binary during that session.
• The key fail-fast is mechanical (re-raises RuntimeError when os.environ.get(k) is empty for either required key); the message names the missing key(s) and points at the README so the operator knows exactly what to fix.

[mergify]

Merge Protections

Your pull request matches the following merge protections and will not be merged until they are valid.

🔴 PR merge requirements

Waiting for

• #approved-reviews-by>=1
• check-success=full-suite-passed

This rule is failing.

• #approved-reviews-by>=1
• check-success=full-suite-passed
• check-success=fastcheck-passed
• check-success~=pre-commit
• title~=(?i)^\[(feat|feature|bugfix|fix|refactor|perf|ci|doc|docs|misc|chore|kernel|new.?model|skill|skills|infra)\]

[gemini-code-assist]

Code Review

This pull request updates the Modal application script to replicate environment validation and setup that is normally handled by the Docker entrypoint but bypassed by @modal.web_server. Specifically, it defines required secret keys, configures environment variables for the native ffmpeg binary and video codec, and adds a runtime check to ensure all required API keys are present before starting the server. The review feedback suggests improving the API key validation by stripping whitespace from the environment variables to ensure whitespace-only keys are correctly identified as missing.

[gemini-code-assist]

Checking not os.environ.get(k) will evaluate to False if the environment variable is set to a whitespace-only string (e.g., " "). Stripping the value and defaulting to an empty string ensures that empty or whitespace-only API keys are correctly caught as missing.

Suggested change

	missing = [k for k in _REQUIRED_SECRET_KEYS if not os.environ.get(k)]
	missing = [k for k in _REQUIRED_SECRET_KEYS if not os.environ.get(k, "").strip()]

[alexzms]

Pushed e1bde40a to address gemini's whitespace nit: not (os.environ.get(k) or "").strip() now collapses unset (None), empty (""), and whitespace-only (" ") values into the "missing" set.