Replace oc with kubectl for standard Kubernetes operations

[agullon]

Summary

Replace oc CLI usage with kubectl for standard Kubernetes operations throughout the codebase. The oc CLI should be retained only where OpenShift-specific subcommands are required (e.g., oc adm release info, oc adm release new, oc adm policy add-scc-to-group).

Motivation

This is an upstream/OKD project designed to work without Red Hat subscriptions. Depending on oc for basic get nodes/pods operations introduces an unnecessary dependency on the OpenShift CLI when kubectl (already bundled with MicroShift) is fully sufficient.

The codebase already uses kubectl in some places (e.g., src/cncf/run_sonobuoy_tests.sh, src/deb/install.sh), creating inconsistency. The DEB install script even creates a symlink from kubectl → oc because oc isn't available on Debian, highlighting this friction.

Scope

Replace oc → kubectl in:

• src/cluster_manager.sh — oc get nodes,pods -A -o wide
• src/quickrpm.sh — oc get pods -A (in echo/usage text)
• src/quickstart.sh — oc get pods -A (in echo/usage text)
• docs/run-bootc.md — oc get nodes, oc get pods -A
• docs/run.md — oc get pods -A
• src/etcd/README.md — oc get nodes, oc get pods -A
• .claude/agents/microshift-deployer.md — "Use kubectl and oc commands" reference

Keep oc as-is in (no kubectl equivalent):

• src/image/prebuild.sh — oc adm release info (OKD release inspection)
• src/okd/build_images.sh — oc adm release new, oc adm release info (OKD image building)
• src/cncf/run_sonobuoy_tests.sh — oc adm policy add-scc-to-group (OpenShift SCC management)

Review and simplify:

• src/deb/install.sh — Currently creates kubectl → oc symlink; after this change, the symlink may no longer be needed for runtime usage (but may still be needed for build-time scripts that use oc adm)

Acceptance Criteria

• All standard Kubernetes CLI invocations use kubectl instead of oc
• oc is only used for OpenShift-specific subcommands (oc adm release info/new, oc adm policy)
• Documentation reflects the change
• make check passes (linters)