feat(mobile): add iOS support to the Expo client

[aurascoper]

Repository topology — read first

This mobile branch is an independent Expo application history and has no
common ancestor with the Swift/macOS main branch. This PR targets
feat/dialect-synthesis intentionally and must not be retargeted to main.
(Longer-term disposition: a separate neuralcompose-client repository.)

What this adds

Universal Android/iOS support for the Expo thin client, on the Expo Go path
(IOS_DEVELOPMENT_PATH=expo-go) — every native module is Expo-Go-bundled; no
custom native code or entitlements. Android package, EAS Android profiles, and
runtime behavior preserved.

• app.json: removed invalid newArchEnabled (SDK 57 schema error), added
  scheme, iOS bundle ID com.aurascoper.neuralcomposeclient, buildNumber /
  versionCode, microphone + local-network usage strings. ATS left fully
  intact — no NSAllowsArbitraryLoads, no exception domains.
• Config: EXPO_PUBLIC_USE_MOCK / EXPO_PUBLIC_SERVER_URL /
  EXPO_PUBLIC_EEG_WS_URL env-driven with pure, tested resolvers; .env.example
  added. Live mode without an endpoint is a visible LIVE · NO ENDPOINT error
  state — never a silent fallback to mock.
• Privacy hygiene: the committed Tailnet IP is scrubbed from source, README,
  reference doc, and test fixtures; a Jest scan guards committed config against
  CGNAT addresses and credential-shaped strings.
• Overview: client data-source pill (MOCK DATA / LIVE /
  LIVE · NO ENDPOINT) — tab headers are hidden, so the previous header badge
  never actually rendered.
• WebSocket: decodeEEGFrame validates shape/finiteness and supports batch
  frames; malformed samples are rejected before the render buffer.
• eegBuffer: bounded push + fixed TP9/AF7/AF8/TP10 channel split extracted
  and unit-tested.
• Deps: expo-asset added (expo-audio peer dependency; expo-doctor failure,
  dev-build crash risk). Jest 30 kept (suite green) and excluded from
  expo install --check.
• eas.json: development + development-simulator profiles added alongside
  the untouched Android profiles.
• Docs: docs/ios-client-audit.md (baseline audit) and docs/ios-client.md
  (workflows, transport security, evidence ledger).

Change stats (current head 69f41f4): 28 changed files, +986 / −73;
closing suite 16 suites / 193 tests.

Historical pre-gate baseline (superseded — kept for the record)

Everything from here through the original evidence table describes the
PRE-ACCEPTANCE state of this PR (original submission 96d3871: 24 files,
+843/−63; 15 suites / 184 tests; Android and audio not yet observed). It is
retained as the historical baseline and is SUPERSEDED by the Gate 4 section
and the "ALL FIVE GATES OBSERVED" acceptance sheet below. No commit-status
checks are attached to any head of this PR — its green state is the recorded
device/simulator evidence plus the local closing suite, not remote CI.

Class	Status
Jest / TypeScript	15 suites / 184 tests pass (2 suites, 3 tests skipped); tsc --noEmit clean; expo-doctor 20/20
Android JS bundle	expo export --platform android green (Hermes 2.1 MB)
Android device	Not run this session (prior Pixel 8a evidence in docs/fable5/)
iOS static export	expo export --platform ios green (bundling + config only)
Native iOS compilation	Not observed (Expo Go path; no prebuild)
iOS Simulator (Expo Go)	Observed — iPhone 17 / iOS 26.5: app launched, all six tabs rendered and navigated, MOCK DATA pill visible, EEG traces in fixed channel order at ~30 fps, mic permission prompt exercised, fast refresh applied live
Physical iPhone	Not observed (no signing configured)
EAS build	Not run (eas whoami: not logged in); profiles configured

Gate 4 — stale/reconnect (OBSERVED, drove commit 886b25f)

Run against a local stub implementing the exact API + /api/eeg/stream WS
schema (8-sample batch frames), with .env.local live mode
(EXPO_PUBLIC_USE_MOCK=false, endpoints on 127.0.0.1:8787), iPhone 17
Simulator via Expo Go:

• Live baseline: LIVE source pill with endpoint host; PrivacyBadge shows
  the stub's server-reported profile; batch WS frames render (proves the
  decodeEEGFrame batch path live, not just in Jest).
• Stale (defect found at 96d3871): with the socket held open but silent,
  the EEG pill stayed green OPEN and the footer read "last frame 0s ago"
  indefinitely — footer age came from flush time, and the flush kept firing on
  retained samples. Overview's "no heartbeat Ns" indicator was already correct,
  and no silent mock substitution occurred anywhere.
• Fix (886b25f): receive-time tracking + flush skip in useEEGStream;
  pure presentStream() helper (unit-tested); EEG pill now shows orange
  STALE Ns with banner "Stream silent — no samples for Ns (socket still
  open)" and an honestly aging "last sample Ns ago" footer. Re-observed live:
  pause → STALE 7s; resume → OPEN.
• Reconnect (PASS on both commits): 2.5 s forced outage → CONNECTING
  (orange) → OPEN; sample counter resumes at normal rate (no doubling);
  server reports exactly 1 WebSocket client after recovery (no duplicate
  streams).

Acceptance sheet — ALL FIVE GATES OBSERVED (2026-07-28, head 69f41f4)

Gate 1 — Android device smoke (Pixel 8a, Expo Go, USB + adb reverse):
launch + all-tab navigation; green MOCK DATA — fixtures on this phone pill
with mock diagnostics; live mode against the reference stub showed the
endpoint identity, fixed TP9/AF7/AF8/TP10 traces at ~30 fps; pause →
STALE 5s + silent-stream banner; drop → red CLOSED + "showing last
cached data" → reconnect to OPEN. PASS.

Gate 2 — Microphone denied (iOS Simulator, re-observed on 69f41f4):
"Microphone access denied" alert, Record visibly disabled, text path intact,
no phantom entry, no crash. PASS.

Gate 3 — Record → stop → persist → play (Pixel 8a): initially FAILED
on both platforms — the Record button was gated on
recorderState.canRecord, which only becomes true after
prepareToRecordAsync(), itself only called by the button (chicken-and-egg;
recording unreachable). Fixed in 69f41f4 (gate on the mount-time permission
result instead). Re-run: recording bar + OS mic indicator → stop → "1 entry
on this device" with duration + Play → entry survives navigation away/back →
playback toggles to Stop. Audio stays in a local file URI; metadata-only in
AsyncStorage. PASS on the new head.

Gate 4 — Stale/reconnect: observed pass (previous section), re-confirmed
on Android hardware during Gate 1.

Gate 5 — Background/foreground (Pixel 8a): 30 s background → foreground:
sample counter advanced 10,520 → 19,976 (~256/s — exactly single-stream
rate, no duplicated sockets/timers), stream resumed OPEN, journal entry
intact, no crash. PASS.

Closing suite on 69f41f4: Jest 16 suites / 193 tests pass, tsc clean,
expo-doctor 20/20, both platform exports green, git diff --check clean.

Still not observed: iOS-simulator audio capture (the fixed button now
enables, but actual recording additionally needs the one-time macOS-level
microphone grant for Simulator — System Settings → Privacy & Security →
Microphone; operator-side). Real-microphone evidence is the Pixel run above.

Useful but not merge blockers for an Expo-Go-scoped PR (remain explicitly
unclaimed):

• EAS login and optional simulator development build
• Physical iPhone test over an HTTPS-reachable Mac endpoint
• Final review of MOCK/LIVE source-pill placement

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