Sidecar diagnostics, docs, and local install flow

[rupertgermann]

Parent

• PRD: Real freemocap sidecar service #68

What to build

Replace the broken sidecar setup path with accurate documentation and user-facing diagnostics for the real local sidecar. Users should know how to install from the supported repo/package path, how to run the sidecar, how to verify health, how to distinguish synthetic vs real hardware mode, and how to troubleshoot camera, calibration, schema, port, and streaming failures.

Acceptance criteria

• Documentation no longer claims that rowing-tracker-sidecar is available from public PyPI unless publishing has actually happened.
• The supported local install and run commands are documented and verified.
• Docs distinguish synthetic/dev mode, real FreeMoCap hardware mode, and any optional public release/publishing path.
• Troubleshooting guidance covers unreachable sidecar, wrong port, incompatible schema, missing cameras, missing calibration, low/zero fps, and stream errors.
• Sidecar logs or diagnostics expose enough context to debug camera discovery, calibration readiness, session start, frame streaming, and session stop failures.
• Licensing/process-boundary notes document the FreeMoCap AGPL dependency and the sidecar-as-separate-process assumption.
• User-facing app errors stay concise while developer logs retain actionable detail.

Blocked by

• Installable sidecar CLI with contract-compatible synthetic source #69
• Real camera health and calibration readiness gate #71
• Start and stop real sidecar capture from Rowing Tracker #72