Native physical execution of UnivMon states and readouts — after #511 #524

Problem

UnivMon passes kernel validation (asap-physical-operators/src/capability.rs:80-95). But the native DAG and readout checks (capability.rs:141-176, :188-222) accept only KLL, DDSketch, HLL and CMS/heap states, and operators/summary/mod.rs:164-169 enforces those checks. So a plan whose one UnivMon state serves distinct, entropy and L2 (#509 Example 2) cannot run natively.

Deliberately deferred when #519 was designed. It is only useful once an accuracy model can certify UnivMon readouts (#523). Otherwise UnivMon is never selected.

Blocked on

Implementation of #511 (unified operator graph: OperatorNode with common metadata, no KeepPreAsap wrappers). Do not start before #511 is implemented.
Physical operators are being redefined by #511 (ASAPOp estimation and readout).

Scope

Accept UnivMon states in the native DAG and readout capability checks. Wire the UnivMon kernel's estimate(), which already supports count, distinct, L2 and entropy, into the summary readout operator. Add an execution test with one state and three readouts.