Integrate Workshop-dependent settings, locale, directive, and hook behavior

[Teakowa]

Parent: #8
Depends on: #35, #36, #52

Goal

Complete the Workshop-dependent behavior that must run after OPY semantic lowering but before the compiler can claim end-to-end compatibility.

Context

The frontend already records settings trees, translation selection, optimization/replacement directives, rule-prefix state, and the post-compile-hook declaration/runtime ABI. workshop-rs owns canonical settings validation/emission, locale mappings, WIR validation, and deterministic localized Workshop emission. This issue connects those existing contracts without duplicating their data.

This issue is the authoritative implementation issue for the backend-dependent parts of these existing matrix features; do not create A-4/A-5/A-6/A-7/A-8/A-9 duplicates:

• semantics/settings-emission
• preprocessing/directive-effects — only effects that survive frontend preprocessing and materially affect Workshop emission/optimization; source preprocessing such as #!define/include state is not reimplemented here.
• hooks/post-compile-workshop
• translations/locale-emission
• optimization/backend-effects

optimization/emission-form is not an opy-rs-owned formatting backend. Canonical Workshop text emission remains owned by workshop-rs; #38 closes the user-visible compiler/evidence contract around that emitter. Output-text identity with OverPy is not a goal.

Scope

• Convert OPY settings HIR into the neutral workshop-rs::settings carrier with source provenance and validate/emit through Workshop-owned tables/contracts.
• Resolve output locale through declared workshop-rs locale/catalog coverage and make missing mappings explicit; do not embed locale spelling tables in opy-rs.
• Define which frontend-recorded optimization/replacement/directive states have observable backend effects required for compatibility and implement only those effects with corpus/oracle evidence.
• Preserve unsupported optimizer/output-form differences as documented non-blocking presentation differences unless observable semantics require them.
• Apply source-level rule-prefix/presentation metadata at the correct lowering/emission boundary without changing source semantic identity.
• Execute #!postCompileHook only after successful final Workshop emission, passing the actual emitted Workshop text to the bounded QuickJS hook ABI and using the hook completion string as the final compiler output.
• Ensure failures in settings/catalog/locale/emission/hook stages produce structured diagnostics with the best available OPY source provenance.
• Add minimized integration fixtures for settings, locale selection, backend directives, and post-compile hooks.

Non-goals

• Reimplementing workshop-rs settings tables, localization corpus, WIR, or emitter.
• Re-running frontend preprocessing such as #!define, #!undef, or include expansion in the backend.
• Matching OverPy optimizer internals, temporary variables, or exact formatting.
• Executing post-compile hooks against WIR, HIR, JSON, or fabricated Workshop text.
• Workshop→OPY reconstruction ([design] Re-evaluate Workshop → OPY reconstruction scope after workshop-rs rebaseline #53 is design-only).

Acceptance criteria

• [integration] Rebaseline opy-compiler on current workshop-rs release #52 and Lower the declared OPY semantic surface into canonical Workshop WIR #36 are complete and integration evidence uses the revalidated Workshop baseline.
• Supported OPY settings lower through Workshop-owned validation/emission with no copied settings/catalog tables.
• Locale selection is catalog-driven and missing mappings/fallbacks are explicit and testable.
• Backend directive/optimizer behavior is evidence-backed and does not overclaim optimizer parity.
• Post-compile hooks receive exactly the final emitted Workshop text and are covered by integration tests.
• optimization/emission-form is closed through the canonical workshop-rs emitter contract plus Expose OPY compilation and close the end-to-end compatibility gate #38 end-to-end evidence, not a second OPY emitter.
• Known Workshop-dependent gaps remain visible in the support matrix until their observable behavior is actually supported.
• Failure paths preserve actionable structured diagnostics and do not silently fall back to guessed semantics.