Lower OPY statements and expressions into canonical Workshop WIR

[Teakowa]

Parent: #36
Depends on: #40 (completed), #52 (completed)

Goal

Close the declared non-catalog OPY statement/expression lowering surface into canonical workshop-rs WIR with explicit, evidence-backed handling of unsupported semantics.

Completion state

• Lower OPY assignment and expression primitives into canonical Workshop WIR #46 — assignment and expression primitives, merged via PR feat(opy-compiler): lower non-control-flow primitives to canonical WIR #54.
• Lower OPY control flow into canonical Workshop WIR with oracle evidence #47 — control flow with oracle evidence, merged via PR feat(opy-compiler): lower control flow into canonical WIR #61 against released workshop-rs 0.1.11.

#47 preserves unsupported/evidence-insufficient cases as explicit source-attributed integration diagnostics rather than silently dropping or guessing semantics. Its pinned oracle coverage includes nested structured switch/control-flow cases and canonical WIR semantic-equivalence checks.

The statement/expression gate is therefore complete. Catalog/member/enum closure remains separately owned by #42.

Explicit non-gating follow-ups remain #58, #59, #60, #65, and wrightkit/workshop-rs#95; their existence does not reopen this completed bounded gate unless later real-project evidence proves one blocks the declared compiler baseline.

Scope satisfied

• Assignment/modification and WIR-representable value lowering through Lower OPY assignment and expression primitives into canonical Workshop WIR #46.
• if, while, supported range for, doWhile, switch, and break handling through Lower OPY control flow into canonical Workshop WIR with oracle evidence #47 with explicit unsupported boundaries where canonical lossless lowering is unavailable.
• Source provenance and structured integration diagnostics preserved.
• Existing canonical WIR used without an OPY-specific Workshop IR.

Non-goals retained

• Catalog-backed builtin/member/enum closure (Close catalog-backed OPY lowering and corpus evidence #42).
• Settings, locale, optimizer directives, post-compile hooks (Integrate Workshop-dependent settings, locale, directive, and hook behavior #37).
• Reconstruction ([design] Re-evaluate Workshop → OPY reconstruction scope after workshop-rs rebaseline #53 design lane).
• Output-text identity with OverPy.

Acceptance evidence

• Lower OPY assignment and expression primitives into canonical Workshop WIR #46 and Lower OPY control flow into canonical Workshop WIR with oracle evidence #47 are complete with independent oracle-backed implementation/test evidence.
• Produced supported WIR is structurally validated and compared through canonical semantic equivalence rather than textual identity.
• Unsupported control-flow shapes remain explicit diagnostics; no source arms/actions are silently discarded.
• Close catalog-backed OPY lowering and corpus evidence #42 remains the next semantic-lowering gate.