Add docs/karaoke-pipeline.md covering the full streaming pipeline from
MPS through unsandbox API to zerotrust container and back. Includes two
Graphviz dot diagrams (rendered to SVG):
- karaoke-pipeline.dot: full system flow across MPS, API, pool, container
- karaoke-ondemand.dot: watch mode on-demand user flow
Update architecture.md feature toggle matrix and related docs table.
Update CLAUDE.md karaoke section with streaming path and on-demand info.
