Update skills for pscale diagnostic CLI commands

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Summary

• Updates the PlanetScale skills to recognize the new read-only pscale insights and pscale inspect diagnostic commands.
• Threads the new CLI evidence surfaces through inventory, Query Insights, schema recommendations, engine safety reviews, the best-practices matrix, the orchestrator, the agent operating model, and the approval contract.
• Preserves the existing safety boundary: diagnostic output is evidence for proposals, not permission to mutate database state.

Changelog entry

• https://planetscale.com/changelog/pscale-insights-inspect-cli

Why

The changelog entry adds read-only CLI commands for production traffic diagnosis and live database health checks. The skills previously referenced MCP/API and older CLI surfaces but did not guide agents to use these new commands or classify their output consistently.

Verification

• git diff --check HEAD^ HEAD
• Validated every numbered SKILL.md has frontmatter and a name field via a local Python script.