[PBT] Exclude pure static empty caches from class statement coverage

[CaelmBleidd]

The class instrumenter rejected an ordinary static empty cache even though the replay contract explicitly excludes module loading from the class statement denominator. Admit only a named static [] allocation with no constructor-property or same-name static-member collision. Its module-loading allocation gets no statement ID; all existing constructor, instance initializer, and reachable method operations retain their original AST IDs and counters. Other static initializers, static blocks, effects, computed members, generators, and unchecked callable reachability keep their existing boundaries.

Validation: all 240 Node adapter tests and all 4 native class replay helper tests pass. The new counter regression fails on the parent instrumenter and passes after restoring this change. It checks that module loading produces no hits, repeated native cache state stays identical, and every constructor/method statement is still credited. Negative tests preserve effectful/spread/nonempty initializers, static blocks, built-in constructor properties, and accessor collisions. git diff --check passes.

All 13 unchanged real-class native smoke scenarios were replayed successfully, including both PGOrbit scenarios. The full instrumented PGOrbit preparation still stops explicitly at CLASS_UNIVERSE_UNSUPPORTED: Unchecked free helper calls cannot establish the selected private callable statement universe. The original source and helper hashes match the frozen manifest. That guard was not relaxed, so this PR establishes the narrow empty-cache measurement contract and does not yet add a fully supported real experiment scenario. Native original replay is not instrumented whole-class replay proof.

Depends on #599.