Add workflow for triaging issues

[swissspidy]

Would be nice to automatically apply the most appropriate labels given the context.

Examples / resources:

• https://github.com/actions/labeler
• https://github.com/actions/ai-inference
• https://github.com/google-github-actions/run-gemini-cli/blob/main/examples/workflows/issue-triage/gemini-triage.yml

This should run whenever a new issues is created, but should also be able to be dispatched manually (where it would find all open issues without a label and trigger the workflow for those)

[swissspidy]

This could probably be done for PRs as well, adding the right command-specific label depending on what area of the code is touched.