Update skills for Query Insights API and Vitess read-only regions

[cursor]

Summary

• Update Query Insights guidance to cover the new public API endpoints for query statistics, per-fingerprint summaries, errors, anomalies, tags/tag groupings, and Postgres traffic budgets affecting a query fingerprint.
• Add read_database service-token guidance for the new Query Insights API surface.
• Update Vitess inventory, review, matrix, and approval-gate guidance for configurable read-only region cluster sizes and replica counts per keyspace.

Changelog entries

• https://planetscale.com/changelog/query-insights-api-endpoints
• https://planetscale.com/changelog/configure-read-only-region-replicas

Why

These changelog entries add new telemetry and topology surfaces that materially affect how the PlanetScale skills should collect evidence, recommend Query Insights/Traffic Control workflows, and gate capacity/topology changes.

Validation

• script/setup /tmp/planetscale-skills-verify