fix: populate LRU for batched invocations in minimal mode response cache

[craigandrews]

Summary

When multiple minimal mode revalidation invocations (different x-invocation-id) arrive concurrently for the same path, the batcher correctly deduplicates them into a single render. However, the LRU is only populated for the invocation that actually rendered. Batched invocations never execute the work function where the LRU write happens. This causes follow-up requests to miss the LRU and trigger a new render, creating a cascade of redundant renders under load.

The fix writes the render result to the LRU for each batched invocation's ID after the batcher promise resolves, so follow-up requests find their entry without re-rendering.

Test Plan

• Unit test: concurrent invocations with different invocationID values verify only one render executes and follow-up requests hit the LRU

[github-actions]

Failing test suites

Commit: 2091e64 | About building and testing Next.js

pnpm test-start test/e2e/app-dir/prefetch-true-instant/prefetch-true-instant.test.ts (job)

• prefetch={true} with instant route > does not include dynamic content in the prefetch when the target route has instant (DD)

Expand output

● prefetch={true} with instant route › does not include dynamic content in the prefetch when the target route has instant

thrown: "Exceeded timeout of 60000 ms for a test.
Add a timeout value to this test to increase the timeout, if this is a long-running test. See https://jestjs.io/docs/api#testname-fn-timeout."

  50 |       }
  51 |
> 52 |       const result = Reflect.apply(target, thisArg, args)
     |                              ^
  53 |       return typeof result === 'function' ? wrapJestTestFn(result) : result
  54 |     },
  55 |     get(target, prop, receiver) {

  at Object.apply (lib/e2e-utils/index.ts:52:30)
  at it (e2e/app-dir/prefetch-true-instant/prefetch-true-instant.test.ts:14:3)
  at Object.describe (e2e/app-dir/prefetch-true-instant/prefetch-true-instant.test.ts:5:1)