fix: ESM-proof the api function imports; inline the OG layout

Follow-up to the repoSocial move — two more tracer/runtime mismatches
kept api/og crashing:

- The package is type:module, so compiled functions run as Node ESM and
  extensionless relative specifiers never resolve. All cross-file api
  imports now carry explicit .js extensions (TS, Vite, and vitest all
  resolve .js -> .ts natively).
- The tracer maps .js specifiers to .ts sources but not .tsx, so an
  imported .tsx module is silently dropped from the bundle. og-layout is
  inlined into the og.tsx entrypoint (entrypoint .tsx compiles fine);
  its exports remain for the tests.

Verified against a local vercel build: both compiled functions import
cleanly under node --input-type=module, and GET on og.js renders a real
200 image/png including the traced JetBrains Mono TTFs.

Author: kevincodex1

api/_lib/og-layout.tsx

@@ -8,7 +8,7 @@ import {
   normalizeRepoOwner,
   repoCacheVersion,
   type RepoSocialInput,
-} from './repoSocial';
+} from './repoSocial.js';
 
 const REPO: RepoSocialInput = {
   name: 'digital-garden',

api/_lib/repoSocial.test.ts

@@ -1,5 +1,5 @@
 import { afterEach, describe, expect, it, vi } from 'vitest';
-import { fetchRepository, type ApiRepository } from './repository';
+import { fetchRepository, type ApiRepository } from './repository.js';
 
 const REPOSITORY: ApiRepository = {
   id: 'repo-1',

api/_lib/repository.test.ts

@@ -1,8 +1,8 @@
 import { afterEach, describe, expect, it, vi } from 'vitest';
 
-import { repoCacheVersion } from '../_lib/repoSocial';
-import type { ApiRepository } from '../_lib/repository';
-import { GET } from '../og';
+import { repoCacheVersion } from '../_lib/repoSocial.js';
+import type { ApiRepository } from '../_lib/repository.js';
+import { GET } from '../og.js';
 
 const repository = {
   id: 'repo-1',

api/_tests/og.test.tsx

@@ -1,8 +1,8 @@
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
-import { fetchRepository, type ApiRepository } from '../_lib/repository';
-import { GET } from '../repo-page';
+import { fetchRepository, type ApiRepository } from '../_lib/repository.js';
+import { GET } from '../repo-page.js';
 
-vi.mock('../_lib/repository', () => ({
+vi.mock('../_lib/repository.js', () => ({
   fetchRepository: vi.fn(),
 }));