feat: add dashboard session trace closure

[Upper9527]

Summary

• add a local dashboard UI/API and CLI commands for syncing and serving the snapshot
• visualize local/shared skills, validation progress, version history, and session traces
• close the local session trace loop by ingesting records/conversations.jsonl and records/prm_scores.jsonl into the dashboard projection
• document dashboard usage in the English and Chinese READMEs

Verification

• python -m unittest -v tests.test_dashboard
• real local dashboard sync/serve against ~/.skillclaw data
• real SkillClaw proxy regression with a live LLM request, then verified the new local sessions appear in the dashboard API