feat: CaseDefinitionRegistry shim — YAML and Java-lambda case definition coexistence

[mdproctor]

Part of epic #24.

Problem

CaseDefinitionRegistry currently receives only YAML-loaded definitions (via YamlCaseDefinitionLoader, #3). Java-annotated (@CaseType) and TaskDefinition-compiled definitions have no registration path.

Scope

• Wire a unified startup sequence: YAML loader runs first, then CDI bean discovery for @CaseType classes, then TaskDefinition compilation
• Define merge/conflict rules: what happens when YAML and Java define the same namespace/name/version key
• Ensure ordering is deterministic and logged clearly at startup

Depends on

• feat: @CaseType CDI qualifier — discover Java-annotated case definition beans #25 (@CaseType — the Java bean source)
• feat: TaskDefinition syntactic sugar — higher-level API compiling to Worker + Binding #26 (TaskDefinition sugar — the compiled source)

Blocks

• feat: @CaseType CDI qualifier — discover Java-annotated case definition beans #25 and feat: TaskDefinition syntactic sugar — higher-level API compiling to Worker + Binding #26 are incomplete without this shim wiring them in