ci: parallelize real-api e2e files

vitest.e2e.config.ts

@@ -19,6 +19,21 @@ try {
   // No .env — fine, the environment may already carry the variables.
 }
 
+const DEFAULT_E2E_MAX_WORKERS = 4
+
+function positiveIntFromEnv(name: string, fallback: number): number {
+  const raw = process.env[name]
+  if (raw === undefined || raw === '') return fallback
+
+  const value = Number(raw)
+  if (!Number.isInteger(value) || value < 1) {
+    throw new Error(`${name} must be a positive integer, got ${JSON.stringify(raw)}`)
+  }
+  return value
+}
+
+const e2eMaxWorkers = positiveIntFromEnv('DSH_E2E_MAX_WORKERS', DEFAULT_E2E_MAX_WORKERS)
+
 export default defineConfig({
   // Same resolution note as vitest.config.ts: bare workspace names resolve
   // through the root tsconfig paths map; the native option cannot do this.
@@ -31,9 +46,10 @@ export default defineConfig({
     testTimeout: 120_000,
     hookTimeout: 30_000,
     retry: 2,
-    // Run e2e files one at a time: the shared internal API key has a small
-    // concurrency quota, and parallel files issue enough simultaneous requests
-    // to trip it (manifesting as flaky rate-limit errors).
-    fileParallelism: false,
+    // Run files in a bounded pool: enough lower-level parallelism to keep CI
+    // and local with-key runs moving, while leaving a resource knob for shared
+    // API quotas (`DSH_E2E_MAX_WORKERS=1` restores serial execution).
+    fileParallelism: e2eMaxWorkers > 1,
+    maxWorkers: e2eMaxWorkers,
   },
 })