Implement namespace scoping for /api/agents

[maazghani]

Addresses #1812 and @EItanya's feedback to implement server side. If this PR lands, I'll wire the UI into it next.

Adds GET /api/agents/{namespace} to work like kubectl get agent -n kagent, and leaving GET /api/agents as kubectl get agent -A.

Re-use existing namespace validation pattern to return invalid namespaces as 400 bad request.

• implemented HandleListAgentsForNamespace handler with tests
• DRY'd out Agent + AgentHarness aggregation logic into a shared helper
• registered route for /{namespace} in server.go
• updated ListAgents to hit path-based /api/agents/${namespace}

Ran e2e tests using kind-backed env successfully, and validated namespace-filtering works.

[maazghani]

Verification performed so far:

$ kubectl get agent -n kagent
NAME                             TYPE          RUNTIME   READY   ACCEPTED
argo-rollouts-conversion-agent   Declarative   python    True    True
cilium-debug-agent               Declarative   python    True    True
cilium-manager-agent             Declarative   python    True    True
cilium-policy-agent              Declarative   python    True    True
helm-agent                       Declarative   python    True    True
istio-agent                      Declarative   python    True    True
k8s-agent                        Declarative   python    True    True
kebab-agent                      BYO                     True    True
kgateway-agent                   Declarative   python    True    True
observability-agent              Declarative   python    True    True
promql-agent                     Declarative   python    True    True
test-agent-dqm5m                 Declarative   go        True    True
test-agent-p8mfv                 Declarative   python    True    True

$ curl -s $KAGENT_URL/api/agents/kagent | jq '[.data[].agent.metadata.name]'
[
  "kebab-agent",
  "test-agent-p8mfv",
  "cilium-manager-agent",
  "istio-agent",
  "k8s-agent",
  "observability-agent",
  "promql-agent",
  "cilium-policy-agent",
  "kgateway-agent",
  "test-agent-dqm5m",
  "argo-rollouts-conversion-agent",
  "helm-agent",
  "cilium-debug-agent"
]

$ curl -s $KAGENT_URL/api/agents/default | jq .
{
  "error": false,
  "message": "Successfully listed agents"
}

$ curl -s $KAGENT_URL/api/agents/invalid!
{"error":"invalid namespace \"invalid!\": a lowercase RFC 1123 label must consist of lower case alphanumeric characters or '-', and must start and end with an alphanumeric character (e.g. 'my-name',  or '123-abc', regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?'): invalid namespace \"invalid!\": a lowercase RFC 1123 label must consist of lower case alphanumeric characters or '-', and must start and end with an alphanumeric character (e.g. 'my-name',  or '123-abc', regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?')"}

[maazghani]

@claude please review as well. Edit: or not

[Copilot]

Pull request overview

This PR adds namespace-scoped agent listing support by introducing a new /api/agents/{namespace} endpoint, wiring it into both the UI’s getAgents action and the Go API client, and adding handler tests to validate the filtering behavior.

Changes:

• Add GET /api/agents/{namespace} route and handler to list Agents/AgentHarnesses restricted to a namespace (with namespace validation).
• Update UI getAgents action to optionally call the namespace-scoped endpoint.
• Extend Go API client to support listing agents for a specific namespace and add handler test coverage.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
ui/src/app/actions/agents.ts	Add optional namespace parameter to getAgents() to call a namespace-scoped agents endpoint.
go/core/internal/httpserver/server.go	Register a new GET /api/agents/{namespace} route.
go/core/internal/httpserver/handlers/agents.go	Implement HandleListAgentsForNamespace with Kubernetes namespace validation and namespace-scoped listing.
go/core/internal/httpserver/handlers/agents_test.go	Add tests ensuring namespace-scoped listing filters both Agents and AgentHarnesses.
go/api/client/agent.go	Add a client method (and interface entry) for listing agents by namespace.

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[maazghani]

Please ignore my force-pushes I forgot to sign the commit(s).

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.