fix(e2e/tanstackstart-react): pin @tanstack/start-plugin-core to unblock CI #46298

Job	Run time
job_get_metadata / Get Metadata	6s
Check PR branches	4s
Build	7m 18s
Check file formatting	38s
Check lockfile	2m 45s
Lint	1m 2s
Browser Unit Tests	1m 43s
Circular Dependency Check	1m 38s
Size Check	2m 9s
Node (22) Unit Tests	1m 30s
Node (24) Unit Tests	1m 34s
Check for faulty .d.ts files	37s
Cloudflare Integration Tests	1m 39s
Node (20) Unit Tests	1m 47s
Node (18) Unit Tests	1m 33s
Prepare E2E tests	2m 58s
Bun Integration Tests	0s
Deno Unit Tests	0s
Bun Unit Tests	0s
Upload Artifacts	0s
Remix (Node ${{ matrix.node }}) Tests	0s
Node (${{ matrix.node }})${{ (((matrix.typescript && format(' (TS {0})', matrix.typescript))) \|\| '') }} Node-Core Integration Tests	0s
Playwright ${{ matrix.bundle }}${{ ((matrix.project && (matrix.project != 'chromium') && format(' {0}', matrix.project)) \|\| '') }}${{ ((matrix.shard && format(' ({0}/{1})', matrix.shard, matrix.shards)) \|\| '') }} Tests	-1s
PW ${{ matrix.bundle }} Tests	-1s
Node (${{ matrix.node }})${{ (((matrix.typescript && format(' (TS {0})', matrix.typescript))) \|\| '') }} Integration Tests	-1s
E2E tunnel-static Test	1m 53s
E2E tunnel-object Test	2m 11s
E2E tunnel-generated Test	2m 8s
E2E tanstackstart-react Test	2m 13s
E2E tunnel-custom Test	2m 2s
E2E ${{ (matrix.label \|\| matrix.test-application) }} Test (optional)	-1s
All required jobs passed or were skipped	6s
	39m 30s

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