feat(recall): add optional remote rerank

[YOMXXX]

Summary

• add optional recall.rerank config for remote /rerank APIs, disabled by default
• over-retrieve L1 candidates before rerank and trim back to recall.maxResults
• apply rerank to both auto-recall injection and tdai_memory_search
• fail open to the original recall order on timeout, API error, or incomplete config

Closes #3.

Verification

• npm test
• npm run build
• npm pack --dry-run (342.0 KB)

[Maxwell-Code07]

感谢您的持续共建！我们会尽快 review 实现，有结果会在这里同步。感谢完善的验证步骤！