fix(today): draw the active ring's own battery in the Liquid header instead of nothing (#2208 second half)

[pipiche38]

#2208 stopped the Liquid Today header drawing the STRAP's charge under an active ring, and the control has shown nothing under a ring since: StrapBatteryDisplay.resolve answered .notActiveDevice for every non-WHOOP active device because it could not tell whose number it held. The ring's own charge was already there — LiveState.ouraBatteryPct on iOS and SourceCoordinator.ouraBatteryPct on Android, both cleared with the link (#2075), both already resolved by LiveConsoleReadout.batteryPercent for the Live console and the Devices list. The header was the one surface still blind to it.

Change

• iOS StrapBatteryDisplay.resolve takes ringPct + ringCharging (no defaults, for the same reason activeIsWhoop has none): a non-WHOOP active device with a ring charge reported this link is .charge(isRing: true); with none it stays .notActiveDevice, so a generic HR strap or a machine — which never write ouraBatteryPct — keep the control off the header exactly as before. Charging under a ring is the ring's charger state (OuraWearState.charging), never the strap's BATTERY_LEVEL bit.
• .charge carries isRing so the VoiceOver label names the device the number belongs to: "Ring battery N percent(, charging)" — "Strap battery" over a ring's charge would be the [oura][ui] Today screen still draws the WHOOP's charge under an active Oura ring — #2076 covered the Live Console, Devices and the widget, not Today #2208 misattribution again, in the label instead of the number. Strings in every catalog locale.
• Android: HeaderBatteryDisplay.resolve, a pure twin of the iOS resolver (minus the charging bit the Android ring never drew), replaces the strapIsActiveDevice gate + raw batteryPct pair on LiquidTodayHeader; LiquidBatteryRing takes isRing for its label (today_ring_battery_percent, every locale).

Design tokens only (the ring's stroke and hues are unchanged); no new colours, fonts or spacing.

Verification

• LiquidBatteryDisplayTests 15/15 under xcodebuild test (Strand, macOS), four new ring cases.
• HeaderBatteryDisplayOracleTest 4/4 — the 60-line expected literal is the verbatim stdout of the Swift enum compiled standalone (swiftc -O) over the whole activeIsWhoop × connected × strap-% × ring-% grid, plus the named [oura][ui] Today screen still draws the WHOOP's charge under an active Oura ring — #2076 covered the Live Console, Devices and the widget, not Today #2208 / battery: say whose charge it is on all seven surfaces, not three #2216 cases.
• Strand (macOS) and NOOPiOS build; compileFullDebugKotlin clean; i18n_audit --ci (both platforms) and doc_comment_lint green.
• Display-only — the values come from the same fields the Live console already shows on hardware. On-device screenshot to follow.

Refs #2208, #2216, #2075.