Add end-to-end coverage for large enclave responses

[Copilot]

Existing stress tests cover large requests and KV writes, but not enclave-generated responses near or above ringbuffer capacity.

Changes

• Add an authenticated, read-only, non-forwarded response generator.
• Read memory.circuit_size and memory.max_msg_size from the active primary's rendered configuration.
• Derive a safe maximum generated response as half of memory.max_msg_size, preserving headroom for QuickJS and response serialization.
• Configure the generator through a member-authenticated endpoint, then verify responses at the configured ringbuffer capacity and derived response cap.
• Verify each response's status, exact size, and boundary bytes before existing KV stress tests run.

Closes #5039

• Fixes Add an end-to-end test that amplifies the response size #5039

[Copilot]

Pull request overview

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Adds end-to-end coverage for enclave-generated HTTP responses at/above the ringbuffer capacity, to complement existing KV stress tests and close #5039.

Changes:

• Added a new readonly, authenticated /batch/generate endpoint that returns a response body of requested size.
• Added an e2e test that requests 16 MiB and 32 MiB responses and verifies status, size, and boundary bytes before existing stress tests.
• Updated the “run to destruction” entrypoint logic to adjust max_msg_size_bytes around the new large-response coverage.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
tests/e2e_batched.py	Adds large-response e2e test and updates max message size configuration around destruction runs.
src/apps/batched/src/batched.js	Adds response generator handler that returns a body of requested size.
src/apps/batched/app.json	Registers the new /batch/generate endpoint with authn/readonly/no-forwarding settings.

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[Eddy Ashton (eddyashton)]

I had pending comments on the test structure, but it looks like I never posted those and they're resolved now? LGTM.