feat: replace transformers.js with direct ONNX WASM for Bun compatibility

- Remove @huggingface/transformers dependency (539MB native binaries)
- Add direct ONNX Runtime Web embedding engine
- Bundle all-MiniLM-L6-v2-q8 model (24MB, no runtime downloads)
- Works with Node.js, Bun, and bun build --compile
- Air-gap compatible: fully self-contained, no internet required

New WASM embedding components:
- WASMEmbeddingEngine: Main integration class
- WordPieceTokenizer: Pure TypeScript tokenizer
- EmbeddingPostProcessor: Mean pooling + L2 normalization
- ONNXInferenceEngine: Direct ONNX Runtime Web wrapper
- AssetLoader: Model file loading

Tests added:
- 11 WASM embedding integration tests
- 8 Bun compatibility tests

New npm scripts:
- test:wasm - Run WASM embedding tests
- test:bun - Run tests with Bun
- test:bun:compile - Build and run compiled binary

tests/integration/bun-compile-test.ts

@@ -0,0 +1,165 @@
+/**
+ * Bun Compile Test
+ *
+ * Tests that Brainy works when compiled with `bun build --compile`.
+ * This verifies:
+ * 1. No native binaries required (pure WASM)
+ * 2. Model is properly bundled
+ * 3. Embeddings work without network access
+ *
+ * To test manually:
+ *   bun build tests/integration/bun-compile-test.ts --compile --outfile /tmp/brainy-bun-test
+ *   /tmp/brainy-bun-test
+ */
+
+import { Brainy } from '../../dist/index.js'
+import { embeddingManager } from '../../dist/embeddings/EmbeddingManager.js'
+import { WASMEmbeddingEngine } from '../../dist/embeddings/wasm/index.js'
+
+async function testBunCompile() {
+  const results: { test: string; passed: boolean; error?: string }[] = []
+
+  console.log('🚀 Brainy Bun Compile Test\n')
+  console.log('Runtime:', typeof Bun !== 'undefined' ? `Bun ${Bun.version}` : `Node.js ${process.version}`)
+  console.log('')
+
+  // Test 1: WASM Engine initialization
+  try {
+    console.log('1. Testing WASM Engine initialization...')
+    const engine = WASMEmbeddingEngine.getInstance()
+    await engine.initialize()
+    console.log('   ✅ WASM Engine initialized')
+    results.push({ test: 'WASM Engine init', passed: true })
+  } catch (error) {
+    console.log('   ❌ WASM Engine failed:', (error as Error).message)
+    results.push({ test: 'WASM Engine init', passed: false, error: (error as Error).message })
+  }
+
+  // Test 2: Generate embedding
+  try {
+    console.log('2. Testing embedding generation...')
+    const engine = WASMEmbeddingEngine.getInstance()
+    const embedding = await engine.embed('Hello from Bun!')
+    if (embedding.length !== 384) {
+      throw new Error(`Expected 384 dimensions, got ${embedding.length}`)
+    }
+    console.log(`   ✅ Generated ${embedding.length}-dim embedding`)
+    results.push({ test: 'Embedding generation', passed: true })
+  } catch (error) {
+    console.log('   ❌ Embedding failed:', (error as Error).message)
+    results.push({ test: 'Embedding generation', passed: false, error: (error as Error).message })
+  }
+
+  // Test 3: Semantic similarity
+  try {
+    console.log('3. Testing semantic similarity...')
+    const engine = WASMEmbeddingEngine.getInstance()
+    const catEmb = await engine.embed('The cat sat on the mat')
+    const felineEmb = await engine.embed('A feline rests on a rug')
+    const stockEmb = await engine.embed('Stock market crash')
+
+    const cosineSim = (a: number[], b: number[]) => {
+      let dot = 0
+      for (let i = 0; i < a.length; i++) dot += a[i] * b[i]
+      return dot // Already normalized
+    }
+
+    const similarSim = cosineSim(catEmb, felineEmb)
+    const dissimilarSim = cosineSim(catEmb, stockEmb)
+
+    if (similarSim <= dissimilarSim) {
+      throw new Error(`Semantic similarity failed: similar=${similarSim.toFixed(4)}, dissimilar=${dissimilarSim.toFixed(4)}`)
+    }
+    console.log(`   ✅ Semantic similarity works (similar: ${similarSim.toFixed(4)} > dissimilar: ${dissimilarSim.toFixed(4)})`)
+    results.push({ test: 'Semantic similarity', passed: true })
+  } catch (error) {
+    console.log('   ❌ Semantic similarity failed:', (error as Error).message)
+    results.push({ test: 'Semantic similarity', passed: false, error: (error as Error).message })
+  }
+
+  // Test 4: EmbeddingManager
+  try {
+    console.log('4. Testing EmbeddingManager...')
+    await embeddingManager.init()
+    const emb = await embeddingManager.embed('Test via manager')
+    if (emb.length !== 384) {
+      throw new Error(`Expected 384 dimensions, got ${emb.length}`)
+    }
+    console.log('   ✅ EmbeddingManager works')
+    results.push({ test: 'EmbeddingManager', passed: true })
+  } catch (error) {
+    console.log('   ❌ EmbeddingManager failed:', (error as Error).message)
+    results.push({ test: 'EmbeddingManager', passed: false, error: (error as Error).message })
+  }
+
+  // Test 5: Full Brainy initialization with fresh memory storage
+  try {
+    console.log('5. Testing Brainy initialization (in-memory)...')
+    const brain = new Brainy({
+      storage: 'memory',
+      storageOptions: { path: ':memory:' }
+    })
+    await brain.init()
+    console.log('   ✅ Brainy initialized')
+    results.push({ test: 'Brainy init', passed: true })
+
+    // Test 6: Add document
+    console.log('6. Testing document add...')
+    const docId = await brain.add({ data: 'Machine learning concepts', type: 'concept' })
+    if (!docId || typeof docId !== 'string') {
+      throw new Error('Document add returned no ID')
+    }
+    console.log(`   ✅ Document added: ${docId}`)
+    results.push({ test: 'Document add', passed: true })
+
+    // Test 7: Search
+    console.log('7. Testing semantic search...')
+    const searchResults = await brain.find('AI')
+    console.log(`   ✅ Search returned ${searchResults.length} results`)
+    results.push({ test: 'Semantic search', passed: true })
+
+    // Test 8: Get document
+    console.log('8. Testing document retrieval...')
+    const retrieved = await brain.get(docId)
+    if (!retrieved) {
+      throw new Error('Document not found')
+    }
+    console.log('   ✅ Document retrieved')
+    results.push({ test: 'Document retrieval', passed: true })
+
+    await brain.close()
+  } catch (error) {
+    console.log('   ❌ Brainy test failed:', (error as Error).message)
+    results.push({ test: 'Brainy operations', passed: false, error: (error as Error).message })
+  }
+
+  // Summary
+  console.log('\n' + '='.repeat(50))
+  console.log('SUMMARY')
+  console.log('='.repeat(50))
+
+  const passed = results.filter(r => r.passed).length
+  const failed = results.filter(r => !r.passed).length
+
+  for (const r of results) {
+    console.log(`${r.passed ? '✅' : '❌'} ${r.test}${r.error ? `: ${r.error}` : ''}`)
+  }
+
+  console.log('')
+  console.log(`Passed: ${passed}/${results.length}`)
+  console.log(`Failed: ${failed}/${results.length}`)
+
+  if (failed > 0) {
+    console.log('\n❌ Some tests failed!')
+    process.exit(1)
+  } else {
+    console.log('\n✅ All tests passed! Brainy works with Bun compile.')
+    process.exit(0)
+  }
+}
+
+// Run tests
+testBunCompile().catch(error => {
+  console.error('Fatal error:', error)
+  process.exit(1)
+})