Kubernetes executor direct tests fail without envtest assets

What happened:

Direct package-level Go tests for the Kubernetes executor are not self-contained. Running go test ./pkg/app/piped/executor/kubernetes -run TestExecutor_ensureSync -count=1 without preinstalled envtest assets fails while starting envtest.Environment with exec: "etcd": executable file not found in $PATH or fork/exec /usr/local/kubebuilder/bin/etcd: no such file or directory.

What you expected to happen:

Direct package tests should either bootstrap envtest prerequisites automatically or skip with a clear message when the assets are unavailable, instead of failing as though the executor logic is broken.

How to reproduce it:

1. Ensure KUBEBUILDER_ASSETS is unset and no local envtest binaries are installed.
2. Run go test ./pkg/app/piped/executor/kubernetes -run TestExecutor_ensureSync -count=1.
3. Observe TestExecutor_ensureSync fail while envtest.Environment starts.
4. Compare that with make test/go, which installs and exports envtest assets via setup-envtest in Makefile before running the Go tests.

Environment:

• piped version: repository checkout on 2026-07-11 (upstream/master fetched to d720a26a during validation)
• control-plane version: Not applicable
• Others: reproduced locally during repository assessment

Summary

Direct Go tests for the Kubernetes executor rely on envtest binaries that are only provisioned by the Makefile wrapper.

Affected Area

pkg/app/piped/executor/kubernetes/sync_test.go, Makefile

Expected Behaviour

The test should either provision envtest requirements or skip with a clear environment-related message.

Actual Behaviour

The test fails at envtest startup when envtest binaries are not available.

Technical Evidence

• pkg/app/piped/executor/kubernetes/sync_test.go creates envtest.Environment directly and calls Start().
• Makefile provisions setup-envtest and exports KUBEBUILDER_ASSETS for make test/go.
• Reproduced failure:
  • go test ./pkg/app/piped/executor/kubernetes -run TestExecutor_ensureSync -count=1
  • Error: Received unexpected error: unable to start control plane itself: failed to start the controlplane. retried 5 times: exec: "etcd": executable file not found in $PATH

Suspected Root Cause

The test assumes envtest binaries are already available, but that prerequisite is encoded only in the Make target and not in the test itself.

Proposed Direction

Add an explicit envtest asset preflight in the test so it either uses available binaries or skips with a clear message when the environment is missing the required assets.

Acceptance Criteria

• Direct go test on the package no longer reports a misleading functional failure when envtest assets are missing.
• make test/go continues to run the test unchanged when envtest assets are provisioned.
• Contributors can distinguish environmental setup issues from real executor regressions immediately.

Start with pkg/app/piped/executor/kubernetes/sync_test.go, especially TestExecutor_ensureSync and its envtest.Environment setup, then compare the asset provisioning in Makefile and the make test/go target. Run the direct go test command with KUBEBUILDER_ASSETS unset. Done means missing envtest assets produce a clear skip or setup message, while make test/go still runs the test with provisioned assets.