PoC: Plugins in separate environments

[leszko]

Based on #241 and #173

This PR extends the plugin support introduced in #241 by running each plugin:

• in its own uv environment
• in a separate process

This allows plugins to have conflicting dependencies without interfering with each other.

demo_plusing_separate_environment.mp4

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Why this PR?

This PR is primarily a proof of concept to demonstrate that:

1. Plugins can run in isolated environments without adding significant complexity.
2. Bringing this to production quality should be straightforward (estimated 1–3 days of work).
3. Performance is comparable to running everything in a single process.
   • Verified on the long-lived pipeline on Linux: output FPS is unchanged.
4. The existing plugin interface mostly survives the move from a shared environment to isolated ones. Only the main daydream-scope dependency needs to be changed, see:
   • https://github.com/yondonfu/scope-test-generator/
   • https://github.com/leszko/scope-test-generator)

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How does it work?

1. During uv daydream-scope install <url>, the plugin code is copied to ~/.daydream-scope/plugins/<plugin-name>
2. Each plugin includes a pyproject.toml that depends on the base plugin dependencies defined in
   worker_env/pyproject.toml.
3. When the pipeline is loaded, a dedicated process is started for each plugin using uv run.
4. Communication between the main process and plugin processes is handled via ZeroMQ.

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Side notes

• This PR also introduces a separate pyproject.toml for each core pipeline, though we may not want to do it
• The ZeroMQ interface between processes is best understood by reviewing
  https://github.com/daydreamlive/scope/blob/rafal/subprocess-3/src/scope/server/frame_processor_proxy.py
• If we decide to pursue this approach, there are still several areas to validate, including:
  • Windows support
  • Electron app compatibility
  • Proper process lifecycle and shutdown handling
• I haven't focused too much on the code, so there is a lot of code that needs refactoring