Dashboard preview blank state

[ericokuma]

Fixes APP-758

Prevents the dashboard preview from going blank during reconciliation when project files are edited externally.

Why this change?
Previously, when validSpec became null during reconciliation, the frontend immediately reflected this, causing the dashboard preview to disappear. This change ensures a smoother user experience by retaining the last valid dashboard state until reconciliation completes.

What was changed?
Implemented a cached selector (createCachedExploreValidSpecSelector) that holds onto the last complete valid explore and metricsView spec. This cached spec is returned when the current response has a missing validSpec and resources are actively reconciling. Once reconciliation is idle, the cache is no longer used, allowing actual invalid states to surface. This selector was integrated into useExploreValidSpec and getExploreValidSpecQueryOptions.

Checklist:

• Covered by tests
• Ran it and it works as intended
• Reviewed the diff before requesting a review
• Checked for unhandled edge cases
• Linked the issues it closes
• Checked if the docs need to be updated. If so, create a separate Linear DOCS issue
• Intend to cherry-pick into the release branch
• I'm proud of this work!

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Linear Issue: APP-758

  

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