feat(EMBEDDINGS-0001): enable local embedder by default and overhaul settings page

- Wire local embedding provider as the default on startup when no profile is configured
- Refactor embedding settings into dedicated service, DTOs, mappers and models
- Rebuild settings page with profile management UI and live test feedback
- Expose index summary (indexed versions + embedding count) on repo endpoints
- Harden indexing pipeline and context search with additional test coverage

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/server/pipeline/indexing.pipeline.test.ts

@@ -12,6 +12,7 @@ import { join } from 'node:path';
 import { JobQueue } from './job-queue.js';
 import { IndexingPipeline } from './indexing.pipeline.js';
 import { recoverStaleJobs } from './startup.js';
+import { EmbeddingService } from '$lib/server/embeddings/embedding.service.js';
 
 // ---------------------------------------------------------------------------
 // Test DB factory
@@ -22,15 +23,21 @@ function createTestDb(): Database.Database {
 	client.pragma('foreign_keys = ON');
 
 	const migrationsFolder = join(import.meta.dirname, '../db/migrations');
-	const migrationSql = readFileSync(join(migrationsFolder, '0000_large_master_chief.sql'), 'utf-8');
+	for (const migrationFile of [
+		'0000_large_master_chief.sql',
+		'0001_quick_nighthawk.sql',
+		'0002_silky_stellaris.sql'
+	]) {
+		const migrationSql = readFileSync(join(migrationsFolder, migrationFile), 'utf-8');
 
-	const statements = migrationSql
-		.split('--> statement-breakpoint')
-		.map((s) => s.trim())
-		.filter(Boolean);
+		const statements = migrationSql
+			.split('--> statement-breakpoint')
+			.map((s) => s.trim())
+			.filter(Boolean);
 
-	for (const stmt of statements) {
-		client.exec(stmt);
+		for (const stmt of statements) {
+			client.exec(stmt);
+		}
 	}
 
 	return client;
@@ -238,7 +245,8 @@ describe('IndexingPipeline', () => {
 		crawlResult: {
 			files: Array<{ path: string; content: string; sha: string; language: string }>;
 			totalFiles: number;
-		} = { files: [], totalFiles: 0 }
+		} = { files: [], totalFiles: 0 },
+		embeddingService: EmbeddingService | null = null
 	) {
 		const mockGithubCrawl = vi.fn().mockResolvedValue({
 			...crawlResult,
@@ -256,7 +264,12 @@ describe('IndexingPipeline', () => {
 			})
 		};
 
-		return new IndexingPipeline(db, mockGithubCrawl as never, mockLocalCrawler as never, null);
+		return new IndexingPipeline(
+			db,
+			mockGithubCrawl as never,
+			mockLocalCrawler as never,
+			embeddingService
+		);
 	}
 
 	function makeJob(repositoryId = '/test/repo') {
@@ -388,6 +401,64 @@ describe('IndexingPipeline', () => {
 		expect(secondSnippetIds).toEqual(firstSnippetIds);
 	});
 
+	it('re-index backfills missing embeddings for unchanged snippets', async () => {
+		const provider = {
+			name: 'test-provider',
+			model: 'test-model',
+			dimensions: 3,
+			embed: vi.fn(async (texts: string[]) =>
+				texts.map(() => ({
+					values: new Float32Array([0.1, 0.2, 0.3]),
+					dimensions: 3,
+					model: 'test-model'
+				}))
+			),
+			isAvailable: vi.fn(async () => true)
+		};
+		const embeddingService = new EmbeddingService(db, provider, 'local-default');
+		const files = [
+			{
+				path: 'README.md',
+				content: '# Hello\n\nThis is documentation.',
+				sha: 'sha-readme',
+				language: 'markdown'
+			}
+		];
+
+		const pipeline = makePipeline({ files, totalFiles: 1 }, embeddingService);
+		const job1 = makeJob();
+		await pipeline.run(job1 as never);
+
+		const firstSnippetIds = (db.prepare(`SELECT id FROM snippets ORDER BY id`).all() as { id: string }[])
+			.map((row) => row.id);
+		expect(firstSnippetIds.length).toBeGreaterThan(0);
+
+		const firstEmbeddingCount = (
+			db.prepare(`SELECT COUNT(*) as n FROM snippet_embeddings WHERE profile_id = 'local-default'`).get() as {
+				n: number;
+			}
+		).n;
+		expect(firstEmbeddingCount).toBe(firstSnippetIds.length);
+
+		db.prepare(`DELETE FROM snippet_embeddings WHERE profile_id = 'local-default'`).run();
+
+		const job2Id = insertJob(db, { repository_id: '/test/repo', status: 'queued' });
+		const job2 = db.prepare(`SELECT * FROM indexing_jobs WHERE id = ?`).get(job2Id) as never;
+		await pipeline.run(job2);
+
+		const secondSnippetIds = (db.prepare(`SELECT id FROM snippets ORDER BY id`).all() as {
+			id: string;
+		}[]).map((row) => row.id);
+		const secondEmbeddingCount = (
+			db.prepare(`SELECT COUNT(*) as n FROM snippet_embeddings WHERE profile_id = 'local-default'`).get() as {
+				n: number;
+			}
+		).n;
+
+		expect(secondSnippetIds).toEqual(firstSnippetIds);
+		expect(secondEmbeddingCount).toBe(firstSnippetIds.length);
+	});
+
 	it('replaces snippets atomically when a file changes', async () => {
 		const pipeline1 = makePipeline({
 			files: [