feat(planner): deploy DDSketch from MILP plans

[milindsrivastava1997]

Summary

• Pin sketch-bench to its current main revision.
• Emit DDSketch quantile plans with a validated alpha.
• Require finite, positive metric value ranges for MILP memory sizing.
• Apply the operator SLA using sketch-bench's native error metric for the selected family.

Validation

• cargo fmt --check
• cargo clippy -p asap_planner --all-targets -- -D warnings
• cargo test -p asap_planner