fix(tts): reduce Matcha mobile memory reservation

[WardLu]

Summary

• replace the upstream 512 MB eager shared-memory reservation with a reproducible 256 MB mobile-compatible WASM while retaining memory growth
• keep the verified 149 MB model data at its existing immutable URL and fetch only the replacement 12 MB runtime
• support immutable per-file resource URLs across download, cache, runtime and CDN smoke paths
• document the Android failure root cause, binary derivation, hashes, rollback and Test/Live impact

Root cause

The official sherpa-onnx v1.13.2 WASM declares an 8192-page (512 MB) minimum shared memory. Together with the 149 MB data package and model initialization this can terminate Android browser workers after a successful download. Merely changing the JavaScript memory option fails because the WASM import itself requires 8192 pages.

Validation

• npm run verify — 41 files / 356 tests passed; public, security, static, build and artifact checks passed
• affected browser E2E — 32/32 passed
• full CDN smoke — data and mobile WASM bytes, SHA-256, Content-Type, GET/HEAD and CORS passed
• restricted 256 MB JS heap + real CDN — initialized one worker and synthesized Chinese/English words and long sentences
• cache regression — unchanged large data file is reused and only the immutable replacement file is requested
• no database/schema/data/RLS/function changes

Release impact

• label: production-impact
• Preview CDN asset is deployed and verified; Production is not deployed or authorized
• configuration impact and rollback are recorded in docs/releases/1.3.12/CONFIGURATION_IMPACT.json
• real Xiaomi/Quark Preview playback remains the final acceptance step

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Project	Deployment	Actions	Updated
shadow-mate	Ready	Preview	Sep 4, 2026 1:40pm UTC