feat(detectors): added analyze_root_cause

[poshinchen]

Description

• analyze_root_cause(session) -- performs deep causal analysis of failures with a 3-tier fallback strategy (direct → pruned → chunked), returning fix recommendations

Key design decisions:

• Standalone functions (no class hierarchy) -- matches strands-evals convention
• Default model: us.anthropic.claude-haiku-4-5-20251001-v1:0
• failures parameter optional on analyze_root_cause()
  • auto-runs detect_failures() if None
• Pre-flight context check + ContextWindowOverflowException catch as backup

Related Issues

N/A

Documentation PR

Type of Change

New feature

Testing

How have you tested the change? Verify that the changes do not break functionality or introduce warnings in consuming repositories: agents-docs, agents-tools, agents-cli

• I ran hatch run prepare

Checklist

• I have read the CONTRIBUTING document
• I have added any necessary tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• My changes generate no new warnings
• Any dependent changes have been merged and published

---

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.