Avoid committing runtime noise in data/data.json

[lindestad]

data/data.json is being updated by runtime telemetry/state and can leak noisy values into feature branches.

We should consider either:

• generating it from a default/template file when needed, or
• keeping only a stable sample/default file tracked and gitignoring the runtime output.

This came up in PR #63, where live IMU/resource values and missing final newline showed up as unrelated diff noise.