[CHORE] AI Issue triaging

[nasaul]

Add AI issue triage via claude-code-base-action

Adds a GitHub Action that automatically triages new issues using Claude AI.

What it does:

• Classifies issues as real_bug, user_error, feature_request, needs_info, or invalid
• Posts a helpful comment (with corrected code for user errors)
• Applies labels (ai-triaged + type/severity labels), creating them if missing
• Skips bot-authored issues

Files:

• .github/workflows/ai-triage.yml — workflow trigger + claude-code-base-action config
• .github/ai-triage-prompt.md — statsforecast domain knowledge + triage instructions

[codspeed-hq]

Merging this PR will not alter performance

✅ 38 untouched benchmarks

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_{Comparing chore/add_ai_triaging (817e0ed) with main (3bf1687)}

[elephaint]

This looks really good already, any preliminary results if you'd run it?