feat(TRUEREF-0020): add embedding profiles, default local embeddings, and version-scoped semantic retrieval

- Add embedding_profiles table with provider registry pattern
- Install @xenova/transformers as runtime dependency
- Update snippet_embeddings with composite PK (snippet_id, profile_id)
- Seed default local profile using Xenova/all-MiniLM-L6-v2
- Add provider registry (local-transformers, openai-compatible)
- Update EmbeddingService to persist and retrieve by profileId
- Add version-scoped VectorSearch with optional versionId filtering
- Add searchMode (auto|keyword|semantic|hybrid) to HybridSearchService
- Update API /context route to load active profile, support searchMode/alpha params
- Extend MCP query-docs tool with searchMode and alpha parameters
- Update settings API to work with embedding_profiles table
- Add comprehensive test coverage for profiles, registry, version scoping

Status: 445/451 tests passing, core feature complete

src/lib/server/embeddings/embedding.service.test.ts

@@ -248,6 +248,99 @@ describe('OpenAIEmbeddingProvider', () => {
 	});
 });
 
+// ---------------------------------------------------------------------------
+// Migration Tests — embedding_profiles table
+// ---------------------------------------------------------------------------
+
+describe('Migration — embedding_profiles', () => {
+	it('creates the embedding_profiles table', () => {
+		const { client } = createTestDb();
+		const tables = client
+			.prepare("SELECT name FROM sqlite_master WHERE type='table' AND name='embedding_profiles'")
+			.all();
+		expect(tables).toHaveLength(1);
+	});
+
+	it('seeds the default local profile', () => {
+		const { client } = createTestDb();
+		const row = client
+			.prepare("SELECT * FROM embedding_profiles WHERE id = 'local-default'")
+			.get() as any;
+		expect(row).toBeDefined();
+		expect(row.is_default).toBe(1);
+		expect(row.provider_kind).toBe('local-transformers');
+		expect(row.model).toBe('Xenova/all-MiniLM-L6-v2');
+		expect(row.dimensions).toBe(384);
+	});
+});
+
+// ---------------------------------------------------------------------------
+// Provider Registry Tests
+// ---------------------------------------------------------------------------
+
+describe('Provider Registry', () => {
+	it('creates LocalEmbeddingProvider for local-transformers', () => {
+		const { createProviderFromProfile } = require('./registry.js');
+		const profile: schema.EmbeddingProfile = {
+			id: 'test-local',
+			providerKind: 'local-transformers',
+			title: 'Test Local',
+			enabled: true,
+			isDefault: false,
+			model: 'Xenova/all-MiniLM-L6-v2',
+			dimensions: 384,
+			config: {},
+			createdAt: Date.now(),
+			updatedAt: Date.now()
+		};
+		const provider = createProviderFromProfile(profile);
+		expect(provider.name).toBe('local');
+		expect(provider.model).toBe('Xenova/all-MiniLM-L6-v2');
+		expect(provider.dimensions).toBe(384);
+	});
+
+	it('creates OpenAIEmbeddingProvider for openai-compatible', () => {
+		const { createProviderFromProfile } = require('./registry.js');
+		const profile: schema.EmbeddingProfile = {
+			id: 'test-openai',
+			providerKind: 'openai-compatible',
+			title: 'Test OpenAI',
+			enabled: true,
+			isDefault: false,
+			model: 'text-embedding-3-small',
+			dimensions: 1536,
+			config: {
+				baseUrl: 'https://api.openai.com/v1',
+				apiKey: 'test-key',
+				model: 'text-embedding-3-small'
+			},
+			createdAt: Date.now(),
+			updatedAt: Date.now()
+		};
+		const provider = createProviderFromProfile(profile);
+		expect(provider.name).toBe('openai');
+		expect(provider.model).toBe('text-embedding-3-small');
+	});
+
+	it('returns NoopEmbeddingProvider for unknown providerKind', () => {
+		const { createProviderFromProfile } = require('./registry.js');
+		const profile: schema.EmbeddingProfile = {
+			id: 'test-unknown',
+			providerKind: 'unknown-provider',
+			title: 'Unknown',
+			enabled: true,
+			isDefault: false,
+			model: 'unknown',
+			dimensions: 0,
+			config: {},
+			createdAt: Date.now(),
+			updatedAt: Date.now()
+		};
+		const provider = createProviderFromProfile(profile);
+		expect(provider.name).toBe('noop');
+	});
+});
+
 // ---------------------------------------------------------------------------
 // EmbeddingService — storage logic
 // ---------------------------------------------------------------------------
@@ -281,23 +374,36 @@ describe('EmbeddingService', () => {
 	it('stores embeddings in snippet_embeddings table', async () => {
 		const snippetId = seedSnippet(db, client);
 		const provider = makeProvider(4);
-		const service = new EmbeddingService(client, provider);
+		const service = new EmbeddingService(client, provider, 'test-profile');
 
 		await service.embedSnippets([snippetId]);
 
-		const rows = client.prepare('SELECT * FROM snippet_embeddings WHERE snippet_id = ?').all(snippetId);
+		const rows = client
+			.prepare('SELECT * FROM snippet_embeddings WHERE snippet_id = ? AND profile_id = ?')
+			.all(snippetId, 'test-profile');
 		expect(rows).toHaveLength(1);
 
-		const row = rows[0] as { model: string; dimensions: number; embedding: Buffer };
+		const row = rows[0] as { model: string; dimensions: number; embedding: Buffer; profile_id: string };
 		expect(row.model).toBe('test-model');
 		expect(row.dimensions).toBe(4);
+		expect(row.profile_id).toBe('test-profile');
 		expect(row.embedding).toBeInstanceOf(Buffer);
 	});
 
 	it('stores embeddings as retrievable Float32Array blobs', async () => {
 		const snippetId = seedSnippet(db, client);
 		const provider = makeProvider(3);
-		const service = new EmbeddingService(client, provider);
+		const service = new EmbeddingService(client, provider, 'test-profile');
+
+		await service.embedSnippets([snippetId]);
+
+		const embedding = service.getEmbedding(snippetId, 'test-profile');
+		expect(embedding).toBeInstanceOf(Float32Array);
+		expect(embedding).toHaveLength(3);
+		expect(embedding![0]).toBeCloseTo(0.0, 5);
+		expect(embedding![1]).toBeCloseTo(0.1, 5);
+		expect(embedding![2]).toBeCloseTo(0.2, 5);
+	});
 
 		await service.embedSnippets([snippetId]);