fix(ci): constrain @types/node to LTS (even) majors and caret ranges in autoheal prompt

[fro-bot]

Summary

The daily autoheal schedule prompted a bump to @types/node 25, which is an odd-numbered (non-LTS) version. The repository only uses even-numbered Node.js LTS releases and pins dependencies with caret ranges, not bare major version numbers.

Updated SCHEDULE_PROMPT in .github/workflows/fro-bot.yaml to note these conventions so future autoheal runs will:

1. Skip odd major versions of @types/node — only LTS (even) releases are valid targets (20, 22, 24, 26, …)
2. Use caret version ranges instead of bare major pins — e.g., ^24.x instead of "25"

This complements the existing Renovate rule in .github/renovate.json5 that already restricts @types/node to even major versions, but adds the constraint at the autoheal prompt level so the fro-bot agent won't create PRs like #127 in the future.

Context

• Triggered by chore(dev): update @types/node 24 → 25 (major) #127 which bumped @types/node to 25 (odd/non-LTS) and pinned to bare major "25"
• The .github/renovate.json5 already has allowedVersions: '/^v?([0-9]*[02468])\\./' for @types/node
• This PR adds the same constraint to the autoheal prompt so fro-bot is aware

Test plan

• Verify the autoheal prompt text is clear and accurate
• Verify that the next daily autoheal run respects the even-major constraint