refactor(integrations): split the provider clients into wire types, endpoints and mappers

Oura, Polar, WHOOP and Strava each keep the transport and endpoints in
`client.ts` and gain `wire-types.ts` (the record shapes) and `map.ts` (the
pure record-to-row mappers, no I/O). Google Health's 1,600-line client
becomes `budget.ts` (slice budget and outcome tally), `request.ts` (error
detail, retry, rate limits), `data-points.ts` (the paginated walker) and a
small `client.ts` for the profile and roll-up reads; its `export * from
"./mappers"` facade is gone and its importers name the module that defines
what they use.

The code moved verbatim; the mapper goldens written before the move and
the provider integration tests pass unchanged.

src/__tests__/baselines/source-function-lines.json

@@ -326,8 +326,8 @@
     "lib/fhir/build-bundle.ts :: buildFhirDocumentBundle": 363,
     "lib/fitbit/sync-core.ts :: upsertFitbitMeasurements": 356,
     "lib/gamification/achievements-result.ts :: buildAchievementsResult": 586,
-    "lib/google-health/client.ts :: forEachDataPointPage": 288,
-    "lib/google-health/client.ts :: forEachDataPointPage > walk": 223,
+    "lib/google-health/data-points.ts :: forEachDataPointPage": 288,
+    "lib/google-health/data-points.ts :: forEachDataPointPage > walk": 223,
     "lib/google-health/sync-core.ts :: upsertGoogleHealthMeasurements": 453,
     "lib/illness/correlation.ts :: computeIllnessCorrelation": 233,
     "lib/import/labs-csv.ts :: importLabsCsv": 309,