Update skills for August PlanetScale CLI changes

[cursor]

Summary

• Update Vitess guidance for CLI-managed read-only regions, including read-only-region inventory, region-scoped password safety, and region-targeted dumps.
• Add VTGate CLI guidance for read-only show/status commands and approval-required resize/cancel actions.
• Update Postgres PgBouncer guidance for switching dedicated replica availability-zone affinity after creation.
• Reflect the new operational safety classifications in the inventory, change-gate, best-practices matrix, and CLI automation skills.

Changelog entries

• https://planetscale.com/changelog/cli-read-only-regions
• https://planetscale.com/changelog/vtgate-resize-cli
• https://planetscale.com/changelog/dedicated-replica-pgbouncer-switch-affinity

Verification

• Markdown-only skill updates; no package manifest or test harness is present.
• Verified branch is pushed and clean after commit a327bcb.