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Query reply API is missing explicit delete reply and needs cleanup for bindings

Query reply API is missing explicit delete reply and needs cleanup for bindings: a task in LegoFlow-SWE (Harbor dataset). Problem The current query reply API is inconsistent and difficult to expose cleanly in language bindings (Rust and Python). In particular:

The task

**Problem** The current query reply API is inconsistent and difficult to expose cleanly in language bindings (Rust and Python). In particular:

Part of Lego-X/LegoFlow-SWE.