Add trace quality checks

[ding-swj]

AgentScope validates trace structure today. The next layer should flag suspicious or incomplete traces.

Possible checks:

• Run has edits but no verification command
• Run has failed tests but no later passed test
• High-risk edits have no evidence notes
• Summary exists but no changed files are recorded

Expected output:

• CLI warnings
• Optional PR summary checklist
• Documentation for quality rules

Non-goals:

• Blocking all trace imports
• Inferring hidden agent reasoning