Enhance Vite configuration for TanStack Start integration

- Updated vitest.config.ts to include a new alias for the TanStack Start server context, improving path resolution.
- Introduced a stub for the TanStack Start server context to streamline server context handling.

These changes enhance the integration of TanStack Start by improving the Vite configuration and server context management.

Author: mantrakp04

packages/template/vitest.config.ts

@@ -1,7 +1,16 @@
+import { fileURLToPath } from 'node:url' // THIS_LINE_PLATFORM template
 import { defineConfig, mergeConfig } from 'vitest/config'
 import sharedConfig from '../../vitest.shared'
 
+const tanstackStartServerContextStub = fileURLToPath(new URL('./src/tanstack-start-server-context.default.ts', import.meta.url)) // THIS_LINE_PLATFORM template
+
 export default mergeConfig(
   sharedConfig,
-  defineConfig({}),
+  defineConfig({
+    resolve: {
+      alias: {
+        "@stackframe/tanstack-start/tanstack-start-server-context": tanstackStartServerContextStub, // THIS_LINE_PLATFORM template
+      },
+    },
+  }),
 )