test(cdk): add executable guard that Lambda bundling is disabled (#366)

PR #371 review finding 1: the ~15× synth speedup rested entirely on the
`disable-bundling.ts` setupFiles entry, but the only regression guards were
honor-system prose (AGENTS.md) and a review_pr.md checklist item. Dropping the
setupFiles wiring, reordering Jest setup, or a CDK rename of the context key
would silently revert the suite to full-bundling synths with no failing check.

Adds two assertions: the synth context carries `aws:cdk:bundling-stacks: []`,
and a bare-App stack reports `bundlingRequired === false`. Verified empirically
against aws-cdk-lib@2.259.0 that without the disable a bare App yields
`bundlingRequired === true`, so these discriminate a real regression.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: scottschreckengaust

cdk/test/setup/disable-bundling.test.ts

@@ -0,0 +1,43 @@
+/**
+ *  MIT No Attribution
+ *
+ *  Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ *  Permission is hereby granted, free of charge, to any person obtaining a copy of
+ *  the Software without restriction, including without limitation the rights to
+ *  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ *  the Software, and to permit persons to whom the Software is furnished to do so.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ *  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ *  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ *  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ *  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ *  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ *  SOFTWARE.
+ */
+
+// Executable guard for the global Lambda-bundling disable (#366).
+//
+// The speedup in this package depends entirely on `test/setup/disable-bundling.ts`
+// running as a Jest `setupFiles` entry. Until now the only regression guards
+// were prose in AGENTS.md and a checklist item in review_pr.md — both
+// honor-system. If someone drops the `setupFiles` wiring, reorders Jest setup,
+// or a CDK rename breaks the context key, the suite silently reverts to a
+// full-bundling (~15× slower) synth with no failing check. These assertions
+// make that floor machine-enforced.
+import { App, Stack } from 'aws-cdk-lib';
+
+describe('global Lambda bundling disable', () => {
+  it('sets aws:cdk:bundling-stacks to [] in the synth context', () => {
+    // A bare `new App()` reads CDK_CONTEXT_JSON, which setupFiles populated.
+    expect(new App().node.tryGetContext('aws:cdk:bundling-stacks')).toEqual([]);
+  });
+
+  it('makes a bare-App stack report bundlingRequired === false', () => {
+    const stack = new Stack(new App(), 'BundlingProbe', {
+      env: { account: '123456789012', region: 'us-east-1' },
+    });
+    expect(stack.bundlingRequired).toBe(false);
+  });
+});