chore(triage-issue): Improve triage prompt for accuracy

[github-actions]

Note

The pull request "chore(triage-issue): Improve triage prompt for accuracy" was created by @s1gr1d but did not reference an issue. Therefore this issue was created for better visibility in external tools like Linear.

Improve the prompt to challenge the framing of the issue reporter and consider misconfiguration etc.

Also fix some issues where the agent was trying to write where it was not allowed in CI (e.g. writing to tmp). I added some general prompts directly to the system prompt in the GitHub action (as it's only relevant for CI).

[linear]

JS-1775