[BUG] Fix k8s_execute_command kubectl exec argv handling and honor container #59

Summary

The Kubernetes k8s_execute_command tool appears broken for typical multi-token commands: the logical command line is forwarded to kubectl exec incorrectly, the optional container parameter is ignored, and failures often surface only as generic exit status 1, which hides stdout/stderr and leads agents astray.

Current behavior

• Commands with operators like | are rejected upfront by validation (potentially dangerous characters detected) — that part may be intentional for a strict safe mode, but it blocks common diagnostics (e.g. ss -tnp | grep 5000).
• Even simple whitespace-separated commands (e.g. echo test, ls -la, which ss, ss -tnp) fail with exit status 1 despite working when invoked manually via kubectl exec … -- ….
• In pkg/k8s/k8s.go, the exec path passes command to kubectl in a way that effectively treats the entire string as a single argument after --, instead of splitting into argv tokens (-- echo test vs -- "echo test").
• The container field from the tool request does not result in kubectl exec -c <container>, so targeting a specific container in a multi-container pod is unreliable.

Expected behavior

• Commands without shell metacharacters should run with kubectl-compatible argv: after --, each token becomes a separate argument (standard kubectl exec … -- cmd arg1 arg2 …).
• When container is set and valid, kubectl exec must receive -c <container>.
• On failure, surface stderr/stdout (and non-zero exit) in the tool result/error path instead of opaque exit status 1 wherever possible.

Versions / scope

Still reproducible in the latest release v0.2.0 and on main (verified 2026-05-16): in pkg/k8s/k8s.go, handleExecCommand still passes the full command string as a single argv element after kubectl exec … -- and does not map the tool parameter container to kubectl exec -c …. The same behavior was already present in v0.1.3 and v0.1.4 — this code path did not change between those tags and v0.2.0 / current main.

A quick search of this repository’s issues/PRs did not find a dedicated report for k8s_execute_command / handleExecCommand (e.g. by name k8s_execute_command); if this duplicates something, please link and close.

Related but distinct: #54 / #55 (Cilium-focused kubectl exec -n). This report is about the general k8s_execute_command contract (argv splitting, -c, and error propagation).

Suggested upstream fix direction

1. Structured API preferred long-term: command + args[], or robust parsing rules documented and tested (avoid ambiguity with quoted args if staying string-only).
2. Honor container → always add -c when non-empty after validation.
3. Keep strict validation by default where appropriate; if shell/pipe features are needed, expose an explicit, opt-in mode (approval / documented risk) rather than silent breakage.
4. Tests: echo test, ls -la, ss -tnp, multi-container pod with -c, plus error cases that assert stderr is visible.