feat(MULTIVERSION-0001): add version management UI and auto-enqueue versions on re-index

- Add POST /api/v1/libs/:id/versions/discover endpoint that calls
  versionService.discoverTags() for local repos and returns empty tags
  gracefully for GitHub repos or git failures
- Enhance POST /api/v1/libs/:id/index to also enqueue jobs for all
  registered versions on default-branch re-index, returning versionJobs
  in the response
- Replace read-only Indexed Versions section with interactive Versions
  panel in the repo detail page: per-version state badges, Index/Remove
  buttons, inline Add version form, and Discover tags flow for local repos
- Add unit tests for both new/changed backend endpoints (8 new test cases)

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

src/routes/api/v1/libs/[id]/versions/discover/server.test.ts

@@ -0,0 +1,160 @@
+/**
+ * Unit tests for POST /api/v1/libs/:id/versions/discover
+ *
+ * Verifies:
+ * - Local repo returns discovered tags
+ * - GitHub repo returns empty tags gracefully (no error)
+ * - Non-existent repo returns 404
+ */
+
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import Database from 'better-sqlite3';
+import { readFileSync } from 'node:fs';
+import { join } from 'node:path';
+
+let db: Database.Database;
+
+vi.mock('$lib/server/db/client', () => ({
+	getClient: () => db
+}));
+
+vi.mock('$lib/server/db/client.js', () => ({
+	getClient: () => db
+}));
+
+vi.mock('$lib/server/pipeline/startup', () => ({
+	getQueue: () => null
+}));
+
+vi.mock('$lib/server/pipeline/startup.js', () => ({
+	getQueue: () => null
+}));
+
+// Mock git utilities so tests don't require a real git repo
+vi.mock('$lib/server/utils/git', () => ({
+	discoverVersionTags: vi.fn(),
+	resolveTagToCommit: vi.fn()
+}));
+
+vi.mock('$lib/server/utils/git.js', () => ({
+	discoverVersionTags: vi.fn(),
+	resolveTagToCommit: vi.fn()
+}));
+
+import { POST as postDiscover } from './+server.js';
+
+const NOW_S = Math.floor(Date.now() / 1000);
+
+function createTestDb(): Database.Database {
+	const client = new Database(':memory:');
+	client.pragma('foreign_keys = ON');
+
+	const migrationsFolder = join(import.meta.dirname, '../../../../../../../lib/server/db/migrations');
+	const ftsFile = join(import.meta.dirname, '../../../../../../../lib/server/db/fts.sql');
+
+	const migration0 = readFileSync(join(migrationsFolder, '0000_large_master_chief.sql'), 'utf-8');
+	const migration1 = readFileSync(join(migrationsFolder, '0001_quick_nighthawk.sql'), 'utf-8');
+	const migration2 = readFileSync(join(migrationsFolder, '0002_silky_stellaris.sql'), 'utf-8');
+
+	for (const migration of [migration0, migration1, migration2]) {
+		for (const stmt of migration
+			.split('--> statement-breakpoint')
+			.map((s) => s.trim())
+			.filter(Boolean)) {
+			client.exec(stmt);
+		}
+	}
+
+	client.exec(readFileSync(ftsFile, 'utf-8'));
+	return client;
+}
+
+function seedRepo(
+	client: Database.Database,
+	overrides: { id?: string; source?: 'github' | 'local'; sourceUrl?: string } = {}
+): string {
+	const id = overrides.id ?? '/facebook/react';
+	client
+		.prepare(
+			`INSERT INTO repositories
+			 (id, title, source, source_url, state, created_at, updated_at)
+			 VALUES (?, ?, ?, ?, 'indexed', ?, ?)`
+		)
+		.run(
+			id,
+			'React',
+			overrides.source ?? 'github',
+			overrides.sourceUrl ?? 'https://github.com/facebook/react',
+			NOW_S,
+			NOW_S
+		);
+	return id;
+}
+
+describe('POST /api/v1/libs/:id/versions/discover', () => {
+	beforeEach(async () => {
+		db = createTestDb();
+		const git = await import('$lib/server/utils/git');
+		vi.mocked(git.discoverVersionTags).mockReset();
+		vi.mocked(git.resolveTagToCommit).mockReset();
+	});
+
+	it('returns 404 when repo does not exist', async () => {
+		const response = await postDiscover({
+			params: { id: encodeURIComponent('/nonexistent/repo') }
+		} as never);
+
+		expect(response.status).toBe(404);
+		const body = await response.json();
+		expect(body.error).toBeDefined();
+	});
+
+	it('returns discovered tags for a local repository', async () => {
+		const { discoverVersionTags, resolveTagToCommit } = await import('$lib/server/utils/git');
+		vi.mocked(discoverVersionTags).mockReturnValue(['v2.0.0', 'v1.0.0']);
+		vi.mocked(resolveTagToCommit).mockImplementation(({ tag }) =>
+			tag === 'v2.0.0' ? 'abc12345' : 'def67890'
+		);
+
+		seedRepo(db, { source: 'local', sourceUrl: '/home/user/myrepo' });
+
+		const response = await postDiscover({
+			params: { id: encodeURIComponent('/facebook/react') }
+		} as never);
+
+		expect(response.status).toBe(200);
+		const body = await response.json();
+		expect(body.tags).toHaveLength(2);
+		expect(body.tags[0]).toEqual({ tag: 'v2.0.0', commitHash: 'abc12345' });
+		expect(body.tags[1]).toEqual({ tag: 'v1.0.0', commitHash: 'def67890' });
+	});
+
+	it('returns empty tags for a GitHub repository (no error)', async () => {
+		seedRepo(db, { source: 'github', sourceUrl: 'https://github.com/facebook/react' });
+
+		const response = await postDiscover({
+			params: { id: encodeURIComponent('/facebook/react') }
+		} as never);
+
+		expect(response.status).toBe(200);
+		const body = await response.json();
+		expect(body.tags).toEqual([]);
+	});
+
+	it('returns empty tags when git discovery throws', async () => {
+		const { discoverVersionTags } = await import('$lib/server/utils/git');
+		vi.mocked(discoverVersionTags).mockImplementation(() => {
+			throw new Error('git command failed');
+		});
+
+		seedRepo(db, { source: 'local', sourceUrl: '/home/user/myrepo' });
+
+		const response = await postDiscover({
+			params: { id: encodeURIComponent('/facebook/react') }
+		} as never);
+
+		expect(response.status).toBe(200);
+		const body = await response.json();
+		expect(body.tags).toEqual([]);
+	});
+});