Close catalog-backed OPY lowering and corpus evidence

[Teakowa]

Parent: #36
Depends on: #41

Goal

Close the catalog-backed portion of OPY semantic lowering and use corpus evidence to determine the supported end-to-end surface before #36 can complete.

Scope

• Lower generic builtin actions/values through manifest catalogId links into canonical workshop-rs identities.
• Lower receiver/member forms and enum/contextual-domain identities without copying Workshop catalog/member/enum tables into opy-rs.
• Implement OPY-specific special lowering only where pinned oracle/corpus evidence requires observable semantics.
• Run structural and canonical-id validation for produced WIR.
• Expand minimized integration fixtures into representative synthetic and real-world corpus cases.
• Classify every remaining Workshop-dependent lowering gap explicitly; advance support-matrix states only where end-to-end evidence exists.

Non-goals

• Settings/locale/backend directive/post-compile-hook behavior (Integrate Workshop-dependent settings, locale, directive, and hook behavior #37).
• Workshop→OPY reconstruction.
• Matching temporary variables, optimizer internals, formatting, or output-text identity.

Acceptance criteria

• Declared builtin/member/enum identities either lower through workshop-rs or remain explicit evidence-backed gaps.
• Representative real-world cases reach deterministic Workshop emission with no unexpected semantic divergence in the supported slice.
• WIR passes Program::validate and canonical catalog validation.
• Compatibility metadata reflects actual evidence; known gaps are never counted as success.
• No authoritative Workshop data is duplicated in opy-rs.
• Lower the declared OPY semantic surface into canonical Workshop WIR #36 can be closed based on objective implementation and corpus evidence.