Expand test coverage once the real Google Health response shape is confirmed

[mregen]

Depends on the rollup-shape verification issue. Add regression tests locking in the verified request/response shape, plus coverage for GoogleHealthApi's 401-triggered refresh path and TokenStore's read/write round-trip.

[mregen]

Partial progress: WeightToolsTests now matches the confirmed-live rollupDataPoints shape (1f01e3d), so that half is done. Still open: coverage for GoogleHealthApi's 401-triggered refresh path and TokenStore's read/write round-trip - neither has tests yet.

[mregen]

Status update: partially done. Regression tests locking in the confirmed rollup response shape now exist for every data type - WeightToolsTests, ActivityToolsTests, HeartRateToolsTests, SleepToolsTests, and BodyFatToolsTests (17 tests total, all passing). Still open: this issue also asks for coverage of GoogleHealthApi's 401-triggered token-refresh path and TokenStore's read/write round-trip - neither has a dedicated test yet. Leaving open, scoped down to just that remaining piece.