chore(prompts): add fix active PR comments prompt with scoped changes (#44996)

## Summary of the Pull Request
Enhance the active PR comments prompt to allow for scoped changes while
removing outdated model references from various prompt files.

## PR Checklist
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx

## Detailed Description of the Pull Request / Additional comments
The changes include the addition of a new prompt for fixing active PR
comments with scoped changes, ensuring that only simple fixes are
applied. Additionally, references to the model 'GPT-5.1-Codex-Max' have
been removed from several prompt files to streamline the prompts.

## Validation Steps Performed
Manual validation of the new prompt functionality was conducted to
ensure it correctly identifies and resolves active PR comments.
```

.github/prompts/fix-issue.prompt.md

@@ -1,6 +1,5 @@
 ---
 agent: 'agent'
-model: 'GPT-5.1-Codex-Max'
 description: 'Execute the fix for a GitHub issue using the previously generated implementation plan'
 ---