Add AI prompt template for CI job failure classification (#4135)

## Summary

Add `JOB_INSIGHT_PROMPT.md` — a structured prompt template for
[jenkins-job-insight](https://github.com/myk-org/jenkins-job-insight) to
classify CI test failures.

### What it provides:
- Classification rules for CODE ISSUE vs PRODUCT BUG vs environmental
- Decision procedure with required evidence structure
- SSH/paramiko known patterns (including paramiko#2568)
- Severity definitions for product bugs
- Code fix guidance for code issues
- Jira search keyword generation rules
- Dependent operator classification (Service Mesh, NMState, SR-IOV,
Descheduler, etc.)
- Cross-failure deduplication guidance
- Repository exploration guide for AI analysis
- Reference links to all relevant upstream repos

Co-authored-by: Claude <noreply@anthropic.com>

Author: rnetser