Integration tests break on Kind 0.32.0 / Kubernetes v1.36.1

We pin Kind to v0.31.0 (Kubernetes node v1.35.0) for the integration tests to keep CI deterministic, and #537 makes CI actually use that pinned version rather than whatever the runner image ships.

Separately, we found the suite fails on Kind 0.32.0 (default node v1.36.1) with attach/timeout errors -- it showed up on #532, #535 and #536, having last been green on #530. We don't yet know why v1.36.1 breaks it. Opening this to track the investigation.

Start by reproducing the integration-test attach and timeout failures with Kind 0.32.0 and Kubernetes node v1.36.1, then compare them with the pinned Kind 0.31.0 and node v1.35.0 setup. Inspect the CI changes from #537 and the failures reported on #532, #535, and #536; done means identifying the cause and restoring a passing, deterministic suite or documenting the blocker.

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