Fix missing twoslash types silently shipping to production

Two fixes for the post-#729 regression where the live aspire.dev site
shipped TS2307 'Cannot find module ./.modules/aspire.js' errors in
rendered HTML:

1. ec.config.mjs: throw instead of warn when .twoslash-types/aspire.d.ts
   is missing. The previous soft fallback let astro build produce broken
   HTML whenever the deploy pipeline didn't run `pnpm twoslash-types`
   first.

2. frontend.esproj: add a BuildFrontendForPublish target that runs
   `pnpm install --frozen-lockfile` and `pnpm run build` before the
   Publish target. The JS SDK's BuildCommand is gated off via
   ShouldRunBuildScript=false (kept that way to keep `aspire run` fast),
   so without an explicit publish-time hook `dotnet publish` would
   package a stale or empty dist/.

Author: slang25

src/frontend/ec.config.mjs

@@ -9,15 +9,17 @@ import { pluginDisableCopy } from './src/expressive-code-plugins/disable-copy.mj
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
 const ASPIRE_TYPES_PATH = resolve(__dirname, '.twoslash-types/aspire.d.ts');
-const aspireTypes = existsSync(ASPIRE_TYPES_PATH)
-  ? readFileSync(ASPIRE_TYPES_PATH, 'utf8')
-  : '';
 
-if (!aspireTypes) {
-  // Non-fatal — twoslash blocks that import the SDK will just show `any`.
-  // Run `pnpm twoslash-types` to refresh.
-  console.warn('[ec] .twoslash-types/aspire.d.ts missing — run `pnpm twoslash-types`');
+// Missing types cause every `import './.modules/aspire.js'` sample to render
+// a TS2307 into the generated HTML. A silent warn here previously shipped
+// that error to prod — fail the build instead so the gap is caught in CI/deploy.
+if (!existsSync(ASPIRE_TYPES_PATH)) {
+  throw new Error(
+    `[ec] .twoslash-types/aspire.d.ts not found at ${ASPIRE_TYPES_PATH}. ` +
+      'Run `pnpm twoslash-types` before `astro build` (the `pnpm build` script chains both).'
+  );
 }
+const aspireTypes = readFileSync(ASPIRE_TYPES_PATH, 'utf8');
 
 /** @type {import('@astrojs/starlight/expressive-code').StarlightExpressiveCodeOptions} */
 export default {
@@ -57,7 +59,7 @@ export default {
         // Virtual files merged into the Twoslash VFS. The Aspire SDK types
         // are declared at `.modules/aspire.ts` so docs samples that import
         // `'./.modules/aspire.js'` resolve against the real API surface.
-        extraFiles: aspireTypes ? { '.modules/aspire.ts': aspireTypes } : {},
+        extraFiles: { '.modules/aspire.ts': aspireTypes },
       },
     }),
   ],

src/frontend/frontend.esproj

@@ -3,8 +3,20 @@
     <PublishAssetsDirectory>$(MSBuildProjectDirectory)/dist</PublishAssetsDirectory>
     <BuildCommand>pnpm run build</BuildCommand>
     <ShouldRunNpmInstall>false</ShouldRunNpmInstall>
-    <!-- Disables running the build (or compile) script located on package.json during Build -->
+    <!-- Disables running the build (or compile) script located on package.json during Build.
+         Keeps `aspire run` / dev `dotnet build` fast; publish runs the build via the
+         BuildFrontendForPublish target below. -->
     <ShouldRunBuildScript>false</ShouldRunBuildScript>
     <IntermediateOutputPath>$(MSBuildProjectDirectory)/obj/$(Configuration)</IntermediateOutputPath>
   </PropertyGroup>
+
+  <!-- Ensure dist/ is freshly produced (and .twoslash-types/aspire.d.ts generated)
+       whenever this project is published. The JS SDK's BuildCommand is gated off above,
+       so without this target a `dotnet publish` would package a stale or missing dist. -->
+  <Target Name="BuildFrontendForPublish" BeforeTargets="Publish">
+    <Message Importance="high" Text="frontend.esproj: running 'pnpm install --frozen-lockfile' before publish" />
+    <Exec Command="pnpm install --frozen-lockfile" WorkingDirectory="$(MSBuildProjectDirectory)" />
+    <Message Importance="high" Text="frontend.esproj: running 'pnpm run build' before publish" />
+    <Exec Command="pnpm run build" WorkingDirectory="$(MSBuildProjectDirectory)" />
+  </Target>
 </Project>