ui: shared ClusterSwitcher + Radar loading icon

[nadaverell]

Summary

• Shared ClusterSwitcher (in @skyhook-io/k8s-ui, re-exported from @skyhook-io/radar-app) replaces two divergent cluster-picker UIs. OSS Radar's ContextSwitcher rewrites on top of it; Radar Hub's HubClusterSwitcher will too in a follow-up Hub PR. Hub's picker previously rendered the raw gke_<account>_<region>_<cluster> context with a Cluster: prefix and no truncation — overflowing into the connection indicator and the view tabs on narrower screens. The primitive enforces max-w-[120px] sm:max-w-[220px] truncate.
• Loading icon swap: replace the generic lucide Loader2 spinner with the Radar-branded SVG (sweep arm + pinging blips) across the auth barrier, connecting/switching overlays, Audit, Cost, Home, Resources, the pod/image filesystem modals, and the traffic-test wizard. SVG lives in @skyhook-io/k8s-ui (exports: ./assets/radar/radar-icon-loading.svg) so Hub consumes the same asset.

Why

The picker divergence wasn't just cosmetic — Hub had no overflow protection, dropped active-session confirmation, dropped search, and would render with a different brand color than OSS once --color-brand-* tokens diverged. Pulling the primitive into k8s-ui means both apps stay in sync, and the OSS rewrite drops ~290 lines.

While here: the OSS ContextSwitcher previously swallowed fetchSessionCounts failures with a console.error and silently switched, killing port-forwards/terminals without warning. It now surfaces a toast.

Notable design decisions

• href on a ClusterSwitcherItem takes precedence over the parent's onSelect — documented in JSDoc rather than hidden behind a discriminated union (two consumers don't justify the type complexity).
• ESC and click-outside listeners attach only while the dropdown is open, so a stacked modal (the active-sessions confirm dialog) doesn't get its escape key intercepted.
• Selection styling uses .selection / .selection-text classes so the active row picks up Hub's brand color, not Radar-blue.
• Status (dot) and badge (right-anchored pill) are rendered in distinct slots so future callers passing both don't collide.

Ship order

@skyhook-io/k8s-ui must publish first (radar-app peer-deps >=1.5.0); then radar-app. Hub's PR will pin the new versions.

Test plan

• npm run tsc clean in web/
• make frontend builds without warnings (other than pre-existing elkjs dynamic-import warning)
• Verify Radar's switcher trigger truncates correctly on a long context (e.g., GKE)
• Verify Radar's connecting/switching overlays render the new icon at the same vertical position
• Verify the search-result count footer ("3 of 12 clusters") appears when filtering

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Note

Medium Risk
Medium risk because it refactors the cluster context-switching UI and interaction flow (selection, grouping, session-confirmation) and replaces loading indicators across multiple views, which could introduce UX regressions or switching edge cases.

Overview
Introduces a reusable ClusterSwitcher component in @skyhook-io/k8s-ui (and re-exports it from both k8s-ui and @skyhook-io/radar-app) to standardize cluster/context picking with search, grouping, keyboard navigation, truncating trigger text, and optional error/footer slots.

Refactors OSS Radar’s ContextSwitcher to use the shared switcher, preserving the active-session confirmation prompt and improving failure handling by surfacing a toast when session-count checks fail (instead of silently switching).

Adds a branded animated Radar SVG loading icon to k8s-ui exports and swaps multiple Loader2 spinners in both k8s-ui (resources loading state) and the web app (auth redirect, connecting/switching overlays, audit/cost/home, filesystem modals, traffic wizard) to use the shared asset.

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