Complete switch lowering for multiple case-local breaks

[Teakowa]

Parent: #157
Discovered during: #170 / PR #171
Real-project evidence: Teakowa/Overwatch-AI-PVE@e0c0721 src/modules/hero_init/dispatcher.opy

Goal

Complete OPY switch lowering so ordinary multi-case switches with case-local break statements preserve OverPy observable semantics through canonical Workshop WIR.

Context

PR #171 advances the pinned OW1 project past its previous parser/catalog frontiers, but compilation now stops with unsupported-integration-surface:

multiple switch breaks with later reachable actions require canonical switch targets

The demonstrated real-project shape is a normal dispatch switch where each case performs actions and then breaks, for example:

switch eventPlayer.init_hero:
    case Hero.REAPER:
        heroInitReaper()
        break
    case Hero.TRACER:
        heroInitTracer()
        break

Current lowering can represent bounded switch/break shapes, but it rejects multiple case-local breaks when actions remain reachable after the first break because it lacks a correct shared switch-exit target. This is an opy-rs compiler/lowering gap, not a workshop-rs catalog or source-language syntax gap.

Scope

• Support multiple case-local break statements in one OPY switch when later cases contain reachable actions.
• Preserve ordinary case selection, fallthrough, default, and break semantics under the existing canonical Workshop WIR contract.
• Preserve source provenance for the affected control-flow lowering and diagnostics.
• Use the pinned OW1 dispatcher as real-project regression evidence in addition to minimized control-flow fixtures.
• Re-run the affected compatibility/conformance and provider compile evidence after the root capability is fixed.

Non-goals

• Adding OPY-specific switch/break nodes to workshop-rs solely to mirror source syntax.
• Requiring compiler-output identity with upstream OverPy when canonical observable semantics are equivalent.
• Weakening the compatibility/conformance baseline or retaining this demonstrated shape as a known gap.
• General control-flow cleanup unrelated to the demonstrated switch-exit capability.

Acceptance criteria

• A switch with multiple cases containing actions followed by break lowers successfully without unsupported-integration-surface.
• Multiple case-local breaks target the correct shared logical switch exit; no later case action executes after a taken break.
• Existing fallthrough/default and nested control-flow behavior remains correct under pinned oracle or equivalent independent evidence.
• The pinned OW1 src/modules/hero_init/dispatcher.opy no longer fails at the multiple-switch-break boundary.
• The pinned OW1 provider compile workflow is rerun and either produces an artifact or exposes the next independently demonstrated owner blocker.
• Existing compatibility/conformance gates show no unexpected regression attributable to this change.
• Independent implementation ablation that disables/simplifies the new shared switch-exit handling makes the relevant minimized and OW1 regression evidence fail again.

Ownership

• OPY switch/break semantics and lowering: opy-rs.
• Canonical Workshop WIR/validation/emission: workshop-rs.

Readiness

Ready. The failing source shape, owner boundary, and required observable behavior are demonstrated by the pinned real project.

[Teakowa]

Completed by PR #173 and carried into main through the #171 stack.

Current evidence satisfies the issue's demonstrated scope: multiple direct case-local break statements lower through the shared switch-exit path; independent action-trace/semantic evidence covers case selection, break, fallthrough, and default behavior; the pinned Overwatch-AI-PVE@e0c0721e827fb60ff9ed9c48fd78221ed7d9ebfc dispatcher advanced past this boundary; and the recorded ablation restored the former unsupported-integration-surface failure for both the minimized regression and pinned provider workflow.

The later filteredArray(Player) blocker was separate and was fixed in the final #171 follow-up. Closing this stale stacked-PR issue as completed.