feat(TRUEREF-0022): complete iteration 0 — worker-thread indexing, parallel jobs, SSE progress

- Move IndexingPipeline.run() into Worker Threads via WorkerPool
- Add dedicated embedding worker thread with single model instance
- Add stage/stageDetail columns to indexing_jobs schema
- Create ProgressBroadcaster for SSE channel management
- Add SSE endpoints: GET /api/v1/jobs/:id/stream, GET /api/v1/jobs/stream
- Replace UI polling with EventSource on repo detail and admin pages
- Add concurrency settings UI and API endpoint
- Build worker entries separately via esbuild

src/lib/server/pipeline/embed-worker-entry.ts

@@ -0,0 +1,93 @@
+import { workerData, parentPort } from 'node:worker_threads';
+import Database from 'better-sqlite3';
+import { EmbeddingService } from '$lib/server/embeddings/embedding.service.js';
+import { createProviderFromProfile } from '$lib/server/embeddings/registry.js';
+import { EmbeddingProfileMapper } from '$lib/server/mappers/embedding-profile.mapper.js';
+import { EmbeddingProfileEntity } from '$lib/server/models/embedding-profile.js';
+import type { EmbedWorkerRequest, EmbedWorkerResponse, WorkerInitData } from './worker-types.js';
+
+const { dbPath, embeddingProfileId } = workerData as WorkerInitData;
+
+if (!embeddingProfileId) {
+	parentPort!.postMessage({
+		type: 'embed-failed',
+		jobId: 'init',
+		error: 'embeddingProfileId is required in workerData'
+	} satisfies EmbedWorkerResponse);
+	process.exit(1);
+}
+
+const db = new Database(dbPath);
+db.pragma('journal_mode = WAL');
+db.pragma('foreign_keys = ON');
+db.pragma('busy_timeout = 5000');
+
+// Load the embedding profile from DB
+const rawProfile = db.prepare('SELECT * FROM embedding_profiles WHERE id = ?').get(embeddingProfileId);
+
+if (!rawProfile) {
+	db.close();
+	parentPort!.postMessage({
+		type: 'embed-failed',
+		jobId: 'init',
+		error: `Embedding profile ${embeddingProfileId} not found`
+	} satisfies EmbedWorkerResponse);
+	process.exit(1);
+}
+
+const profileEntity = new EmbeddingProfileEntity(rawProfile as any);
+const profile = EmbeddingProfileMapper.fromEntity(profileEntity);
+
+// Create provider and embedding service
+const provider = createProviderFromProfile(profile);
+const embeddingService = new EmbeddingService(db, provider, embeddingProfileId);
+
+// Signal ready after service initialization
+parentPort!.postMessage({
+	type: 'ready'
+} satisfies EmbedWorkerResponse);
+
+parentPort!.on('message', async (msg: EmbedWorkerRequest) => {
+	if (msg.type === 'shutdown') {
+		db.close();
+		process.exit(0);
+	}
+
+	if (msg.type === 'embed') {
+		try {
+			const snippetIds = embeddingService.findSnippetIdsMissingEmbeddings(
+				msg.repositoryId,
+				msg.versionId
+			);
+
+			await embeddingService.embedSnippets(snippetIds, (done: number, total: number) => {
+				parentPort!.postMessage({
+					type: 'embed-progress',
+					jobId: msg.jobId,
+					done,
+					total
+				} satisfies EmbedWorkerResponse);
+			});
+
+			parentPort!.postMessage({
+				type: 'embed-done',
+				jobId: msg.jobId
+			} satisfies EmbedWorkerResponse);
+		} catch (err) {
+			parentPort!.postMessage({
+				type: 'embed-failed',
+				jobId: msg.jobId,
+				error: err instanceof Error ? err.message : String(err)
+			} satisfies EmbedWorkerResponse);
+		}
+	}
+});
+
+process.on('uncaughtException', (err) => {
+	parentPort!.postMessage({
+		type: 'embed-failed',
+		jobId: 'uncaught',
+		error: err instanceof Error ? err.message : String(err)
+	} satisfies EmbedWorkerResponse);
+	process.exit(1);
+});