Foundations, accessibility, and objective fixes across the app

[mmazzarolo]

Follow-up to #136. 28 commits, grouped below. Two of them are deliberately easy to drop — see Judgement calls at the end.

bun run validate:static passes at every commit (80 tests, up from 38). All four Maestro flows pass against an Android release build with R8 enabled — the shrunk build nothing had exercised since the Compose settings screen landed. The iOS splash work was verified on a clean simulator in both appearances.

Foundations

These went first because they change the ground everything else stands on.

• strict: true. expo/tsconfig.base sets no strict, no strictNullChecks, no noImplicitAny, so none of the guarding the code already did was checked. It compiles clean with the flag on — no source changes were needed.
• noUncheckedIndexedAccess. 19 sites. One was a real latent crash: exercise-screen.tsx read currentStep.id unguarded while useExerciseLoop types it as possibly undefined; only the one-second floor on inhale/exhale durations prevented it, which was accidental. Most of the rest were better expressed as types — PatternSteps is now a 4-tuple and patternPresets a non-empty tuple, so the fallback needs no assertion.
• animate() honours its easing argument. It was assigned after the config spread, so every easing a caller passed was silently discarded and the whole app ran one curve.
• A semantic colour layer. colors.ts was a palette with no light/dark pairing, so nine files re-derived the mapping by hand with isDarkMode && styles.xDark — the direct cause of every missing dark variant. themeColors gives each role a value per scheme, and colors.test.ts computes WCAG ratios and asserts them.
• One contract for the settings UI. settings-ui.d.ts declared a shape nothing was assigned to, so TypeScript never compared the three platform files. Three behaviours had already drifted. All three now satisfy SettingsUIModule, and a parity test renders iOS and web through the same assertions.

Bugs fixed

• Settings reads retry once, so a transient failure no longer causes the next settings change to overwrite a still-good payload. Write failures now log instead of vanishing.
• The web picker lost its field name — it spread the shared props into each option row, then overrode label, so "Voice" never reached the screen. Caught by the new parity test on its first run.
• Turning off "use system theme" flipped the wrong way. Defaults are shouldFollowSystemDarkMode: true with theme: "light", so a user on a dark phone who switched it off to keep dark was flipped to light.
• The close button was invisible in light mode — lightgray on the light background is 1.37:1 against a 3:1 requirement, and it is the only way out of a running session.
• Short steps stopped the breathing circle. Animated.stagger started the label fade-out at duration − 400 ms with both fades sharing one value; below 800 ms the fade-out interrupted the fade-in and stopTogether took the circle with it. Measured at a 500 ms step: the circle held 0.078 instead of 1.00 and stopped at 98 ms — while the composite still reported finished: true. 800 ms was broken too.
• Control Center paused your session. The AppState listener fired on any non-active state; iOS reports inactive for Control Center, the app switcher and unanswered call banners.
• Both bell cues were the same sound, so an eyes-closed user could not tell inhale from exhale, and cueBell2 never played at all in the presets with no holds.
• iOS drew two splash screens. expo-splash-screen treats image as a logo to centre; with imageWidth unset it rendered splash.png in a 100 pt box, then the JS overlay drew the same artwork full-bleed. Both layers now draw the same thing, and both gained a dark variant.

Accessibility

The app had zero uses of accessibilityLiveRegion, announceForAccessibility and AccessibilityInfo, so a session could not be followed without sight, and eight rotating circles (sixteen in dark mode) ran regardless of Reduce Motion.

• Steps, the countdown, the last breath and completion now announce.
• Reduce Motion swaps the rotating stack for a single steady circle and drops the slides. The rhythm survives intact because the voice and haptic already carry it.
• The guided voice starts for screen-reader users as a render-time override — the stored setting is not written. Gated off web, because react-native-web answers true to isScreenReaderEnabled() for every browser.
• The timer stays visible past the limit and says Last breath rather than fading out of the accessibility tree.
• The star field holds still under Reduce Motion; it was the last continuous motion left, on the screen where those users spend the whole session.

Content and assets

• Added Coherent (5.5-0-5.5-0) and Extended Exhale (4-0-6-0); renamed deep-calm to 4-7-8 Deep Calm so the best-known pattern in the app is findable. Preset ids are unchanged — normalizePersistedSettingsState validates the stored id against this list, and a changed id would silently reset every existing user to Square.
• Deleted 19 unreferenced files and de-duplicated the two byte-identical app icons. This is repository weight, not binary size: expo-updates is not installed, so assetBundlePatterns is inert and Metro bundles only what require() reaches.

Judgement calls for the reviewer

• eb8294b re-encodes the audio. Laura's lines go from stereo 320 to mono 128 kbps. Defensible for speech, but these are paid voice-actor recordings and it is a listening call, not a measurement. Kept as its own commit so git revert eb8294b drops it alone.
• enableFullScreenImage_legacy is documented by the plugin as a transition helper that will be removed. It is one line and it works today. The durable replacement is a centred wordmark logo used by both layers, which would also fix the iPad crop — that changes how the launch looks, so it is left as a decision.

Known gap, not fixed

Android's stepper buttons still have no accessible name, so TalkBack reads "−" and "+" with no context. It cannot be fixed with the current @expo/ui API: the semantics modifier takes only contentType, FilledTonalButton exposes no content description, and Icon — the one component that accepts one — needs a vector drawable rather than a text glyph. The reason is written into the file at the call site.

Not attempted

Maestro in CI, the home screen restyle, and the breathing curves. The last two are taste work and are better done with eyes on them.