fix(android): keep composer synchronized with IME

[duoyi88]

Closes #194

Root cause

On edge-to-edge Android, adjustResize no longer moves the composer above the IME. The KeyboardAvoidingView change proposed in #182 improves the layout, but a physical Pixel 11 Pro test still left the input partially covered.

A larger keyboardVerticalOffset can correct the open position, but React Native 0.81.5 handles Android keyboardDidHide as another frame-change event. With a non-zero offset, that leaves stale bottom padding after the IME closes, so the composer does not return to the bottom.

Change

• Preserve the existing iOS KeyboardAvoidingView padding behavior and 90 dp offset.
• On Android, initialize from Keyboard.metrics(), subscribe to keyboardDidShow / keyboardDidHide, and apply the IME-reported height directly as bottom padding.
• Reset Android padding explicitly to zero on hide.
• Subscribe before resynchronizing native metrics so an IME transition during route mount cannot be lost.
• Add regression coverage for show, hide, invalid metrics, iOS isolation, and the measured Pixel geometry.

Physical-device verification

Pixel 11 Pro, Android 17:

• Play v0.4.15 reproduced Android: chat input hidden behind keyboard #194 with both Gboard and a custom Trime IME.
• The fix: keyboard/composer (#156), auto-scroll (#155), dead SSE (#186), blocked SSE startup (#189), stale transcripts, uncopyable text, axis-perfect table scrolling, 50-session list cap, transcript flash, dark-mode contrast #182-style build moved the composer but still left 106 px of the input behind the IME.
• The first complete-header-offset build fixed opening but exposed stale padding after keyboard dismissal.
• The final APK was installed over the side-by-side test package and verified by the reporter: opening the IME keeps the full composer visible; dismissing it returns the composer to the bottom.

Verification

• npm test — 339 passed
• npm run typecheck
• Keyboard offset tests — 6 passed
• Android arm64 release APK build
• Physical Pixel 11 Pro open/close cycle

The change is limited to the session keyboard integration and its small pure helper/tests.

[taras-tarabanov]

Verified on CMF Phone 2 Pro, Android 16, Gboard.

Built from v0.4.15 tag + this PR merged, self-signed release APK, server is opencode serve on the same phone via Termux (http://127.0.0.1:4096).

Before: composer fully hidden behind keyboard (issues #194/#156). After: full composer + send button stay visible above the keyboard, typing is readable. It sits flush with no bottom gap, which is fine. Dismissing the keyboard returns the composer cleanly to the bottom, no stuck padding after 3+ open/close cycles.

One build note: npx expo prebuild --clean silently dropped android:usesCleartextTraffic="true" from the manifest even though app.json sets it, so http:// URLs failed instantly in the fresh build until I added a small config plugin forcing the attribute. Might be worth folding into this PR or a follow-up, otherwise clean-prebuild releases will hit it too.