implement filtering AgentList by namespace

[maazghani]

addresses #1812

The agents page showed a single unscoped list across namespaces, which made the view noisy in multi-tenant clusters and harder to navigate. This change adds namespace-aware filtering to the existing agents page without changing the underlying data flow.

• Namespace-scoped list state

  • Adds a namespace selector to the agents page header.
  • Sources the active filter from the namespace query param so the view persists across refresh/navigation.
  • Includes an explicit All namespaces option.

• Consistent filtering across views

  • Applies the namespace filter before rendering, so both AgentGrid and AgentListView stay in sync.
  • Derives available namespace options from the loaded agent set rather than introducing a separate fetch path.

• Filtered empty state

  • Preserves the existing global empty state when no agents exist at all.
  • Adds a namespace-specific empty state when the selected namespace has no matching agents, with a one-click reset to clear the filter.

• Coverage

  • Adds component tests for:
    • URL-driven namespace filtering
    • namespace-filtered empty state behavior

const namespaceFilter = searchParams.get("namespace") || ALL_NAMESPACES;

const filteredAgents =
  namespaceFilter === ALL_NAMESPACES
    ? agents || []
    : (agents || []).filter(
        (item) => (item.agent.metadata.namespace || "") === namespaceFilter,
      );

[Copilot]

Pull request overview

This PR adds namespace-aware filtering to the Agents page UI by deriving the active namespace from the namespace query parameter and applying the filter consistently across both grid and list views, including a namespace-specific empty state.

Changes:

• Add a namespace selector to the Agents page header, driven by the namespace URL query param (with an “All namespaces” option).
• Filter the rendered agents list prior to passing data into AgentGrid / AgentListView, keeping both views consistent.
• Add Jest component tests covering URL-driven filtering, default-namespace normalization, and the filtered empty state.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
ui/src/components/AgentList.tsx	Adds namespace query-param state, namespace dropdown options derived from loaded agents, filtered rendering, and a namespace-specific empty state.
ui/src/components/tests/AgentList.test.tsx	Adds component tests for namespace filtering behavior and filtered empty state.
ui/jest.setup.ts	Updates next/navigation mocks to reusable jest fns so tests can override return values.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[maazghani]

@copilot thoughts on solutions for if the cluster has a large number of namespaces?