Wire /api/v1/validators and add a network validator-dominance bar chart page block

[JSONbored]

The backend ships a network-wide validator leaderboard at GET /api/v1/validators (handleGlobalValidators) that no UI fetches (query count = 0). Surfacing it as a new cross-subnet validator-dominance chart is higher-touch: it needs a new query + type + normalizer, a new route/page or a substantial home block, and careful pagination/empty handling — larger than a single reuse-a-chart bounty and better owned by a maintainer to decide placement (new /validators route vs home block).

Deliverables

• Add a GlobalValidators type + normalizer + globalValidatorsQuery to src/lib/metagraphed/queries.ts calling /api/v1/validators
• Add a validator-dominance chart (BarMini or the new dominance-treemap) ranking operators by cross-subnet footprint/stake share
• Decide and implement placement (new route repo-ui/src/routes/validators.tsx or an Explorer/home block) — architectural call
• Handle cold/empty leaderboard and pagination
• Full unit coverage of the normalizer and chart mapping including empty branches

References

• repo/workers/request-handlers/entities.mjs (handleGlobalValidators @236)
• repo-ui/src/lib/metagraphed/queries.ts
• assessment/gapMatrix.md (Table A: GET /api/v1/validators, flagged unused leaderboard)

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📸 Required: before/after screenshots (this is a UI change)

Non-negotiable. PRs that change UI must include a before/after screenshot table. PRs without it are automatically closed — no exceptions.

Rules:

• Show every page/feature you changed — before and after, one row each.
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|---|---|---|
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size: M · maintainer-only (owner)

[linear-code]

JSO-2103