docs(test/e2e): scrub stale useFixture references

Update the createGetFixture JSDoc and .claude/rules/e2e.md to reflect
the createGetFixture rename and add runFileExistsTest to the helper
list so future readers see the actual API.

Author: wyattjoh

.claude/rules/e2e.md

@@ -131,7 +131,7 @@ In CI, use `bunx playwright install chromium --with-deps` to include system-leve
 
 Fixture files run in parallel (concurrency controlled by the runner, defaults to CPU count). Each fixture uses an isolated temp directory and `CLERK_CONFIG_DIR`, so there is no shared mutable state. Do not use `test.concurrent` within individual fixture files.
 
-Within each test file, `useFixture()` runs `setupFixture()` once in `beforeAll` and shares the result with both the build test and browser test. This avoids duplicating the expensive setup.
+Within each test file, `createGetFixture()` runs `setupFixture()` once in `beforeAll` and shares the result with both the build test and browser test. This avoids duplicating the expensive setup.
 
 ## Adding a new fixture
 
@@ -143,7 +143,7 @@ Within each test file, `useFixture()` runs `setupFixture()` once in `beforeAll`
 Helper functions are in `test/e2e/lib/`:
 
 - `fixture-setup.ts` - `setupFixture`
-- `fixture-test.ts` - `useFixture`, `runFixtureTest`, `runBrowserTest`
+- `fixture-test.ts` - `createGetFixture`, `runFixtureTest`, `runFileExistsTest`, `runBrowserTest`
 - `dev-server.ts` - `startDevServer` (allocates a port internally and retries on collision), `killDevServer`, `buildDevCommand`
 - `test-user.ts` - `createTestUser`, `deleteTestUser`
 - `logger.ts` - `log`, `debug` (shared logging; set `CLERK_E2E_DEBUG=1` for verbose output)

test/e2e/lib/fixture-test.ts

@@ -156,7 +156,7 @@ export function createGetFixture(fixtureDir: string, config: FixtureConfig): Get
 
 /**
  * Register a bun test that verifies the framework build command and
- * `tsc --noEmit` both pass using the shared fixture from `useFixture()`.
+ * `tsc --noEmit` both pass using the shared fixture from `createGetFixture()`.
  *
  * Build runs first so frameworks that generate types during build
  * (TanStack Router routeTree.gen) have them available for tsc.