Native PMM navigation hides Explore from Viewer users

[steveweb7]

Problem

The native PMM navigation shows the existing Explore item only when user.isEditor is true. Consequently, an authenticated Grafana user with the Viewer role cannot discover Explore even when the server explicitly permits Viewer users to use it via [users] viewers_can_edit = true.

Expected behavior

When exploreEnabled is enabled, every authenticated PMM user, including a Viewer, should see the existing Explore navigation item. Anonymous users must remain excluded.

Reproduction

1. Configure Grafana with viewers_can_edit = true.
2. Log in to PMM as a Viewer.
3. Observe that Explore is absent from the native PMM navigation.

Proposed change

In ui/apps/pmm/src/contexts/navigation/navigation.provider.tsx, replace the user.isEditor condition that gates Explore with !user.isAnonymous. This changes only PMM navigation; Grafana datasource, folder, dashboard, and save permissions remain enforced by Grafana.

Validation

• An authenticated Viewer sees Explore when exploreEnabled is true.
• An anonymous user does not see Explore.
• Explore remains hidden when exploreEnabled is false.