Build Wisp: on-device transcription studio (web + native, one codebase)

Private, offline speech-to-text that runs Whisper on the user's own device —
free, no account, no per-minute fees. Replaces Otter.ai / Rev.

- Pure, tested engine: chunking, overlap timestamp-stitching, exports
  (SRT/VTT/TXT/MD/JSON), WAV codec, resampler, job queue, model catalog (142 tests).
- Platform-abstracted TranscriptionEngine: transformers.js on web (loaded from
  CDN at runtime to dodge Metro's onnxruntime-web bundling limits), whisper.rn
  on native. Shared pipeline orchestrates decode -> chunk -> transcribe -> stitch.
- Cross-platform StorageRepo (Dexie web / expo-sqlite native), Zod-validated.
- UI: library + search, import, live-progress transcription, synced click-to-seek
  editor, multi-format export; model picker + privacy in settings.
- Web ships as a single-page PWA with COOP/COEP isolation for threaded WASM;
  Docker (nginx) image + Traefik compose for wisp.briggen.dev.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/lib/types.ts

@@ -0,0 +1,49 @@
+// Core domain types shared across the whole transcription engine.
+// Kept tiny and dependency-free so every pure module can import from here
+// without pulling in React Native, Expo, or any platform code.
+
+/** Whisper always works at 16 kHz mono. */
+export const WHISPER_SAMPLE_RATE = 16000 as const;
+
+/**
+ * A contiguous transcribed segment. Times are in SECONDS and, once a media
+ * file has been fully processed, ABSOLUTE to the whole media (post-stitch).
+ * Engine implementations emit chunk-local times (0-based per chunk); the pure
+ * pipeline offsets and stitches them into absolute time.
+ */
+export interface Segment {
+  /** Inclusive start time in seconds. */
+  start: number;
+  /** Exclusive end time in seconds. */
+  end: number;
+  /** Recognized text for this segment (already trimmed). */
+  text: string;
+  /** Optional confidence in [0,1], derived from avg token logprob when available. */
+  confidence?: number;
+}
+
+/** Decoded audio ready for Whisper: 16 kHz, mono, normalized to [-1, 1]. */
+export interface PcmAudio {
+  readonly sampleRate: typeof WHISPER_SAMPLE_RATE;
+  readonly samples: Float32Array;
+}
+
+/** The Whisper model variants we expose. `.en` = English-only (smaller/faster). */
+export type ModelId =
+  | 'tiny.en'
+  | 'tiny'
+  | 'base.en'
+  | 'base'
+  | 'small.en'
+  | 'small';
+
+export interface TranscribeOptions {
+  modelId: ModelId;
+  /** ISO language code; undefined => auto-detect (multilingual models only). */
+  language?: string;
+  /** Translate the result to English (multilingual models only). */
+  translate?: boolean;
+}
+
+/** Which compute backend an engine resolved to, for UX and model gating. */
+export type Backend = 'coreml' | 'metal' | 'cpu' | 'webgpu' | 'wasm';