[codex] Port review diff surface to Android

[HorusGoul]

Summary

Closes #4.

Adds an Android implementation of T3ReviewDiffSurface for the mobile review diff native module. The Android view decodes the same row/theme/style/token JSON contract as iOS, renders file headers, hunks, code lines, notices, and comments on a custom canvas, supports token patches/reset keys, collapsed/viewed/selected state, initial row scroll, and emits visible-range/draw debug events for incremental highlighting.

Also registers the module for Expo Android autolinking and makes ReviewSheet tolerate missing native view registration with a raw diff fallback instead of force-unwrapping the native surface.

Local Benchmark

Ran a temporary Vite+ benchmark against the shared review diff pipeline that feeds both native implementations. This is not a device render benchmark; it measures parse, adapter, bridge serialization, and JavaScript highlighter costs in Node.

Dataset sizes:

• small: 5 files, 490 native rows, 25.0 KiB diff, 142.4 KiB rows JSON
• medium: 20 files, 4,840 native rows, 254.5 KiB diff, 1,453.6 KiB rows JSON
• large: 40 files, 19,280 native rows, 1,029.4 KiB diff, 5,847.9 KiB rows JSON

Observed p50 timings:

• small parse/build/stringify: 0.27 ms / 0.56 ms / 0.16 ms
• medium parse/build/stringify: 2.48 ms / 6.13 ms / 1.48 ms
• large parse/build/stringify: 9.20 ms / 26.15 ms / 6.39 ms
• medium visible highlight for 360 rows: 20.13 ms p50
• medium full token stream: 529.10 ms p50, intentionally chunked/background work

Takeaway: diff parsing and bridge serialization are not the bottleneck on this synthetic workload. Syntax highlighting dominates; keeping it visible-range driven is important for large diffs. Native iOS-vs-Android draw timing still needs an on-device harness using the emitted draw-metrics / visible-range events.

Validation

• vp check passes with existing lint warnings
• vp run typecheck
• vp run lint:mobile passes; local ktlint and detekt are not installed, so the script skipped those checks as designed
• vp test
• vp run --filter @t3tools/mobile typecheck
• vp run --filter @t3tools/mobile test -- --run nativeReviewDiffSurface.test.ts

[github-actions]

Android APK preview

A self-contained Android preview APK was built for this PR.

• Artifact: t3code-preview-release-pr-7
• Size: 80.8 MiB
• SHA-256: ae3d135eea2f2313508d8176c3a2e301e6a462f2fdcac32341339789ce854899
• Source: d32d9098e94d
• Note: GitHub Actions downloads artifacts as zip archives.

Re-add the android:apk-preview label to build a fresh APK.