fix(k8s): describe the scope and image columns k8s_get_resources actually has

[garlicKim21]

Summary

k8s_get_resources is described as "Get Kubernetes resources using kubectl".
Two behaviours an agent cannot infer are missing from that line, and both
produced wrong answers for me this week with a third-party agent.

1. Default scope is the tool's own namespace, not the cluster.

Asked to check the cluster, the agent called
k8s_get_resources{resource_type: "pod"} and received only the namespace kagent
runs in. It reported that as the cluster and concluded nothing needed attention.
"Query all namespaces (true/false)" says what the flag does — never what
omitting it means.

2. -o wide shows images for workloads but not for pods.

After the agent's discovery instructions were widened, it surveyed pods across
all namespaces — a listing whose columns are
NAME/READY/STATUS/RESTARTS/AGE/IP/NODE and no image. With no version anywhere
in what it had read, the model supplied a plausible one for a DaemonSet-deployed
CNI that was actually running a quite different version, and every comparison
after that was confidently wrong, with no signal until a human noticed.

Notably, helm/agents/k8s/templates/agent.yaml in the main repo already tells
its own agent "Always prefer wide output unless specified otherwise". That
knowledge lives in one agent's prompt; every other agent has to rediscover it by
failing.

all_namespaces typing

all_namespaces is declared as a string and was compared with == "true", so a
model emitting a JSON boolean had --all-namespaces dropped silently and got a
single-namespace answer with no error — the same symptom as (1), but with the
agent asking correctly. The main repo's own e2e mock
(go/core/test/e2e/mocks/invoke_inline_agent.json) passes it as a boolean.

mcp.ParseBoolean uses cast.ToBool, which accepts both spellings, so the
string form keeps working and the schema stays as it is. Happy to change the
declared type instead if you would rather fix it at the schema — that felt like
a compatibility call for maintainers.

Testing

TestHandleKubectlGetEnhanced gains three cases: all_namespaces as a string
and as a boolean both reach kubectl as --all-namespaces, and false keeps the
query namespaced. go build ./..., go test ./pkg/k8s/ and go vet ./pkg/k8s/
pass.

Verified against kagent tools 0.2.1 as shipped — the deployed MCP server
reports the one-line description and all_namespaces typed as string.