Lower the declared OPY semantic surface into canonical Workshop WIR

[Teakowa]

Parent: #8
Depends on: #35 (completed)

Goal

Complete the declared OPY semantic lowering surface into valid canonical workshop-rs WIR and close this stage with representative corpus evidence.

#35 established the dedicated opy-compiler boundary against published workshop-rs = "=0.1.1". This issue is an acceptance gate rather than a single implementation PR.

Current execution state

• Lower OPY program structure into canonical Workshop WIR #40 — Lower OPY program structure into canonical Workshop WIR
• Lower OPY statements and expressions into canonical Workshop WIR #41 — Lower OPY statements and expressions into canonical Workshop WIR
  • Lower OPY assignment and expression primitives into canonical Workshop WIR #46 — Assignment and expression primitives
  • Lower OPY control flow into canonical Workshop WIR with oracle evidence #47 — Control flow with oracle evidence
• Close catalog-backed OPY lowering and corpus evidence #42 — Close catalog-backed OPY lowering and corpus evidence

Intended order: #46 → #47 → close #41 → #42. Keep each branch/PR independently reviewable.

Scope

• Map the currently declared OPY semantic program into existing canonical workshop-rs WIR nodes without introducing another Workshop IR.
• Preserve source provenance and structured failure behavior across the integration boundary.
• Resolve canonical Workshop identities through workshop-rs; never copy authoritative catalog/member/enum data into opy-rs.
• Implement OPY-specific special lowering only where observable behavior is backed by pinned oracle/corpus evidence.
• Use wir::Program::validate and canonical catalog validation as correctness gates.
• Close with representative synthetic and real-world corpus evidence, keeping unsupported cases explicit.

Non-goals

• Settings, locale selection, backend directive effects, and #!postCompileHook execution (Integrate Workshop-dependent settings, locale, directive, and hook behavior #37).
• Workshop→OPY reconstruction.
• Output-text identity, upstream temporary-variable allocation, or optimizer-internal parity.
• A provider-neutral backend abstraction or temporary Workshop IR.

Acceptance criteria

• Lower OPY program structure into canonical Workshop WIR #40, Lower OPY statements and expressions into canonical Workshop WIR #41, and Close catalog-backed OPY lowering and corpus evidence #42 are complete with independent implementation/test evidence.
• Every HIR node claimed by the current frontend support matrix either lowers to valid canonical WIR or is explicitly classified as a remaining evidence-backed Workshop-dependent gap.
• Produced WIR passes structural and canonical-id validation.
• Source provenance remains attached through integration diagnostics and WIR nodes where supported by the public contract.
• Canonical builtin/member/enum existence is decided through workshop-rs, not duplicate local data.
• Representative real-world corpus cases reach deterministic Workshop emission with no unexpected semantic divergence in the supported slice.
• Compatibility states advance only when explicit end-to-end evidence exists.