feat(spo2): surface WHOOP 5.0 spo2_candidate_82 behind experimental toggle (#103) - #1185

…#103 follow-up) (#1186)

Follow-up to #1185. Two Android nits found on re-review:

- The Blood Oxygen tile's candidate captions in HealthVitalsLogic were RAW string
  literals ("Estimate (unverified)" / "toggle ON · no @82 data") — hardcoded English
  that the i18n audit doesn't catch (it misses literals returned from logic-file
  functions, not just @composable Text). Extracted both to strings.xml via uiString
  and translated across the shipped locales (de/es/fr/pt-PT/zh), matching iOS which
  already used String(localized:).
- Wording parity: Android said "Estimate (unverified)"; iOS says "strap estimate
  (unverified)". Aligned Android to the iOS wording so the tile reads the same.

Also collect spo2CandidateByDay reactively in HealthScreen (collectAsStateWithLifecycle
instead of .value), matching VitalSignsScreen, so the Latest-readings card recomposes
on its own when the candidate map updates rather than only incidentally via `days`.

Android-only, display-only, no behavior/scoring change. compileFullDebugKotlin +
i18n_audit --ci both green.

…oggle (ryanbr#103) (ryanbr#1185)

WHOOP 5.0/MG does not write spo2Sample (the ratio-of-ratios SpO₂ path is 4.0-only);
it emits a strap-computed candidate at byte @82 of the v18 historical record. This
surfaces that nightly `spo2_candidate_82` mean in the Blood Oxygen tile as a
"strap estimate (unverified)" fallback when no calibrated spo2Pct exists, behind a
DEFAULT-OFF experimental toggle (Settings → Diagnostics).

Display-only and rule-compliant (CLAUDE.md derived-biosignal): the value is written
to metricSeries as "spo2_candidate" under the "-noop" computed ID, NEVER to spo2Pct,
and never feeds recovery or illness scoring. The @82 candidate has SPLIT cross-device
evidence (+0.99 over 8 nights, but 2 nights opposite on the original device — device/
firmware variance unresolved), so it ships off-by-default and labelled unverified.
Uses the pre-existing, parity-tested AnalyticsEngine.nightlySpo2CandidateMean helper.

Rebased onto current main + fixed to land cleanly:
- HealthScreen.kt: hoisted `NoopPrefs.spo2CandidateDisplay(LocalContext.current)` out of
  the `remember {}` calculation lambda — a @composable read there is a hard compile error
  (the reason the PR's Android build was red).
- Baselined the experimental toggle's title + blurb on both platforms in
  i18n_audit_baseline.json (deferred localization for experimental copy).

Co-authored-by: evoveotech <evoveotech@users.noreply.github.com>

…ryanbr#103 follow-up) (ryanbr#1186)

Follow-up to ryanbr#1185. Two Android nits found on re-review:

- The Blood Oxygen tile's candidate captions in HealthVitalsLogic were RAW string
  literals ("Estimate (unverified)" / "toggle ON · no @82 data") — hardcoded English
  that the i18n audit doesn't catch (it misses literals returned from logic-file
  functions, not just @composable Text). Extracted both to strings.xml via uiString
  and translated across the shipped locales (de/es/fr/pt-PT/zh), matching iOS which
  already used String(localized:).
- Wording parity: Android said "Estimate (unverified)"; iOS says "strap estimate
  (unverified)". Aligned Android to the iOS wording so the tile reads the same.

Also collect spo2CandidateByDay reactively in HealthScreen (collectAsStateWithLifecycle
instead of .value), matching VitalSignsScreen, so the Latest-readings card recomposes
on its own when the candidate map updates rather than only incidentally via `days`.

Android-only, display-only, no behavior/scoring change. compileFullDebugKotlin +
i18n_audit --ci both green.

The previous commit said SpO2 comes from neither strap and the v18 byte-82
value is never shown. That is wrong: since ryanbr#1185 (2026-08-09) the
default-off Settings toggle "Experimental · Blood Oxygen" surfaces its
nightly mean in the Blood Oxygen tile as "strap estimate (unverified)".
A 4.0 has no such byte. It still never feeds scoring, and the NOOP
Limitations grid's "No" predates the toggle by a day.

Analysis migration required: no (documentation only).