chore: update pi runtime dependencies

[corwinm]

Summary

• Updates Pi runtime package family to 0.79.8: @earendil-works/pi-coding-agent, @earendil-works/pi-tui, and @earendil-works/pi-ai.
• Updates adjacent dev tooling patches: vitest 4.1.9, @types/node 24.13.2, and refreshed lockfile resolution.
• Clears the high-severity @earendil-works/pi-coding-agent audit findings plus the Vite/Undici audit findings pulled through the previous tooling graph.

Audit notes

• npm audit now reports 0 high/critical findings.
• Remaining findings are 13 moderate advisories through @changesets/cli → @manypkg/get-packages → read-yaml-file → js-yaml.
• npm audit fix --force proposes downgrading @changesets/cli to 2.6.0, so I left that out of this focused Pi runtime/security update.

Test plan

• npm run ci
• npm audit --json reviewed after the update