fix: resolve WASM loading for Bun --compile single-binary executables

Both roaring-wasm and candle-wasm now work correctly in all environments:
- Node.js (fs.readFileSync)
- Bun runtime (Bun.file)
- Bun --compile (embedded assets via import { type: 'file' })
- Browser (fetch)

roaring-wasm:
- Created src/utils/roaring/index.ts wrapper
- Uses browser bundle which has WASM embedded as base64
- Top-level await ensures initialization before use
- Zero environment detection needed (works everywhere)

candle-wasm:
- Created src/embeddings/wasm/wasmLoader.ts universal loader
- Uses Bun's import { type: 'file' } to embed 93MB WASM in compiled binary
- Fixed browser detection (Bun defines 'self', check for 'document' instead)
- Simplified CandleEmbeddingEngine.ts to use wasmLoader

Binary size verification:
- Minimal Bun binary: 100MB (runtime only)
- Brainy binary: 199MB (100MB runtime + 93MB WASM + 6MB JS)
- No duplication: WASM embedded exactly once

Test results:
- Node.js: 1190/1190 tests pass
- Bun runtime: 8/8 tests pass
- Bun --compile: 8/8 tests pass

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/utils/metadataIndex.ts

@@ -24,7 +24,7 @@ import {
   ZoneMap
 } from './metadataIndexChunking.js'
 import { EntityIdMapper } from './entityIdMapper.js'
-import { RoaringBitmap32 } from 'roaring-wasm'
+import { RoaringBitmap32, roaringLibraryInitialize } from './roaring/index.js'
 import { FieldTypeInference, FieldType } from './fieldTypeInference.js'
 
 export interface MetadataIndexEntry {
@@ -202,6 +202,9 @@ export class MetadataIndexManager {
    * This must be called after construction and before any queries
    */
   async init(): Promise<void> {
+    // Initialize roaring-wasm library (browser bundle requires async init)
+    await roaringLibraryInitialize()
+
     // Load field registry to discover persisted indices (v4.2.1)
     // Must run first to populate fieldIndexes directory before warming cache
     await this.loadFieldRegistry()