ci: auto-label needs-discussion on externally-raised Issues

[jamietanna]

Changes

We're seeing an increase in (LLM-generated) Issues being created on the
project, which is not our contribution model.

As a way to reduce the time of maintainers to manually label these when
we see them, we can automagically determine this based on existing
access to the repo.

Using Triage+ allows any collaborators on the Renovate project to raise
Issues unimpeded.

Context

Please select one of the below:

• This closes an existing Issue: Closes #
• This doesn't close an Issue, but I accept the risk that this PR may be closed if maintainers disagree with its opening or implementation

AI assistance disclosure

Did you use AI tools to create any part of this pull request?

Please select one option and, if yes, briefly describe how AI was used (e.g., code, tests, docs) and which tool(s) you used.

• No — I did not use AI for this contribution.
• Yes — minimal assistance (e.g., IDE autocomplete, small code completions, grammar fixes).
• Yes — substantive assistance (AI generated non‑trivial portions of code, tests, or documentation).
• Yes — other (please describe): Claude Sonnet 4.6

Documentation (please check one with an [x])

• I have updated the documentation, or
• No documentation update is required

How I've tested my work (please select one)

I have verified these changes via:

• Code inspection only, or
• Newly added/modified unit tests, or
• No unit tests but ran on a real repository, or
• Both unit tests + ran on a real repository

The public repository:

[RahulGautamSingh]

lgtm

[jamietanna]

I've not tested this yet, but let's see what happens!

[github-actions]

🎉 This PR is included in version 43.123.1 🎉

The release is available on:

• GitHub release
• 43.123.1

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