fix: pivot hover description in public URL

[royendo]

https://www.loom.com/share/d91d85f0717a42098f424f7631f7eb39

1. d49b584 — Fix fromProto.ts deserialization

Problem: When pivot state is deserialized from a protobuf (e.g. loading a shared/public URL), the mapDimension and mapMeasure
helpers in fromPivotProto weren't copying the description field onto the PivotChipData objects. So chips lost their tooltip
descriptions.

Fix: Added description: dim?.description and description: mes?.description to the two mapping functions (2 lines).

2. d9a348f — Fix convertPresetToExploreState.ts deserialization

Problem: The first commit only fixed one deserialization path (fromProto.ts). The regular explore mode uses a different path —
convertPresetToExploreState.ts — which also builds PivotChipData objects via mapPivotEntry. That path had the same missing
description bug.

Fix: Added description: m.description and description: d.description in the measure and dimension branches of
fromPivotUrlParams (2 lines).

3. daf5dfd — Reactive enrichment in PivotDisplay.svelte

Problem: On public URL first load, the metricsView data (which contains the descriptions) loads after the pivot state is
already deserialized. So even with commits 1 and 2, descriptions are still missing because the dimension/measure metadata isn't
available yet at deserialization time.

Fix: In PivotDisplay.svelte, builds a reactive descriptionMap from $validSpecStore (the metricsView). An enrichDescriptions()
function backfills any chip that's missing a description. The enriched pivot state is passed to PivotHeader and PivotSidebar
instead of the raw $dashboardStore.pivot. This ensures descriptions appear as soon as the metricsView loads, regardless of
timing.

TL;DR: All 3 commits fix the same bug — pivot chip description tooltips being lost — but across three different code paths:
proto deserialization, URL state deserialization, and a race condition on initial load.

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!

[royendo]

flaky e2e

[royendo]

Addressed feedback: removed description from the deserialization mappers in fromProto.ts and convertPresetToExploreState.ts. The reactive enrichment in PivotDisplay.svelte is now the single source for chip descriptions — the mappers only populate id and type.