Address Copilot review: fix redundant lookup and validate env vars

- Extract run_command to local variable to avoid redundant lookup
- Add validation for missing env vars in vite.config.ts with clear error

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ksroda-sa

samples/react/login-pkce/vite.config.ts

@@ -11,6 +11,12 @@ const exposedEnvVars = [
 
 export default defineConfig(({ mode }) => {
   const env = loadEnv(mode, process.cwd(), "");
+  const missing = exposedEnvVars.filter((key) => !env[key]);
+  if (missing.length > 0) {
+    throw new Error(
+      `Missing required env vars: ${missing.join(", ")}. Copy .env.example to .env and fill in the values.`,
+    );
+  }
   return {
     plugins: [react()],
     define: Object.fromEntries(

scripts/extract-snippets.ts

@@ -206,16 +206,15 @@ async function main() {
         snippets[scenarioId] = {};
       }
 
+      const runCommand = manifest.scenarios[scenarioId]?.run_command;
       snippets[scenarioId][fw] = {
         steps: allSteps,
         framework: fw,
         lib: manifest.lib,
         lib_version: getLibVersion(scenarioDir, frameworkDir),
         install: getInstallCommand(scenarioDir),
         repo_path: `samples/${path.relative(SAMPLES, scenarioDir)}`,
-        ...(manifest.scenarios[scenarioId]?.run_command && {
-          run_command: manifest.scenarios[scenarioId].run_command,
-        }),
+        ...(runCommand ? { run_command: runCommand } : {}),
       };
     }
   }