Support duckdb's asof join syntax
Support duckdb's asof join syntax: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). Describe the solution you'd like
The task
**Describe the solution you'd like**
Part of FineEnvs/MiMo-V2.6-RL-harbor-code.