feat: add reproducible Evaluation + Optimization pipeline

[Adonis-a233]

Summary

Implements the reproducible Evaluation + Optimization closed loop for the issue
"设计并实现可复现的 Evaluation + Optimization pipeline".
Related Issue Resolves #91

What Changed

• Added/updated examples/optimization/eval_optimize_loop/
• Implemented six-stage pipeline:
  1. baseline train/val evaluation
  2. failure attribution
  3. prompt optimization
  4. candidate validation
  5. configurable acceptance gate
  6. JSON/Markdown audit persistence
• Added fake mode with fake model / fake judge / trace-mode evalsets.
• Added live mode wiring for AgentOptimizer.optimize and TargetPrompt.add_path.
• Added prompt snapshots and sample optimization_report.json/.md.
• Added Yun callback prompt example using TargetPrompt.add_callback.

Validation

Fake mode:

python examples/optimization/eval_optimize_loop/run.py --mode fake

[github-actions]

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Codecov Report

✅ All modified and coverable lines are covered by tests.
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Additional details and impacted files

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[Adonis-a233]

I have read the CLA Document and I hereby sign the CLA