Schema-driven agent

Goal: create only documented Chain JSON and render it without inventing effect or parameter names.

1. Read the public effect catalog.
2. Constrain output with the Chain v1 schema.
3. Run effetune chain validate chain.json.
4. Run effetune render input.wav output.wav --preset chain.json.

Runtime validation still enforces duplicate IDs, assets, and cross-field rules. MCP, measurement, resampling, ffmpeg, LUFS, and true-peak tools are not v0.1 capabilities.