fix: resolve FFmpeg MIME type error and persist core files in IndexedDB

[Copilot]

loadFFmpeg created blob URLs without MIME types, causing browsers to reject the core JS as a module script (Expected a JavaScript-or-Wasm module script but the server responded with a MIME type of ""). Additionally, FFmpeg core+WASM were re-downloaded on every use.

MIME type fix

Blobs are now wrapped with correct MIME types before createObjectURL:

const ensureMimeType = (blob: Blob, mimeType: string): Blob =>
  blob.type === mimeType ? blob : new Blob([blob], { type: mimeType });

const coreURL = URL.createObjectURL(ensureMimeType(core, 'text/javascript'));
const wasmURL = URL.createObjectURL(ensureMimeType(wasm, 'application/wasm'));

IndexedDB caching

• src/lib/services/idb.ts — Extracted shared openDB from respackStorage.ts. DB version bumped 1→2 to add ffmpeg object store.
• src/lib/services/ffmpegStorage.ts — Key-value blob storage for FFmpeg files, reusing the shared DB.
• src/lib/services/respackStorage.ts — Now imports openDB from idb.ts.
• src/lib/player/services/ffmpeg/index.ts — loadFFmpeg(core?, wasm?) now checks IndexedDB cache first, downloads and caches on miss, and caches caller-provided blobs. This also fixes the existing bug where utils.ts called loadFFmpeg() with no arguments against a signature that required them.
• src/routes/(app)/+page.svelte — Simplified to just await loadFFmpeg() since caching is handled internally.

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Project	Deployment	Actions	Updated (UTC)
player	Ready	Preview, Comment	Mar 21, 2026 5:41pm