feat: @CaseType CDI qualifier — discover Java-annotated case definition beans

[mdproctor]

Part of epic #24.

Port io.casehub.annotation.CaseType from casehub-poc's casehub-core/src/main/java/io/casehub/annotation/.

What it does

A CDI @Qualifier that annotates a class as a case definition implementation for a named case type. The engine uses it during startup to discover Java-implemented case definitions alongside YAML-loaded ones.

Scope

• Port the @CaseType(value) annotation into io.casehub package (home TBD: api/ or app-local)
• Wire CDI bean discovery at startup: scan for beans annotated with @CaseType and register them via CaseDefinitionRegistry
• Decide package home — api/ if other consumers are likely, app-local if not

Depends on

• feat: CaseDefinitionRegistry shim — YAML and Java-lambda case definition coexistence #27 (registry shim) — @CaseType beans need to coexist with YAML definitions in the registry