refactor: make routing system extensible with provider/builder interfaces

BREAKING: LLMRouter now requires explicit LLMProvider

New Abstractions:
- LLMProvider interface: swap providers (OpenAI, Claude, local, etc)
- SpecBuilder interface: custom spec generation strategies
- ParameterBinder interface: flexible parameter resolution
- ActivityExecutor interface: pluggable activity execution
- WorkflowValidator interface: composable validation

Provider System:
- ProviderRegistry: manage multiple LLM providers
- RoutingProviderLLM: fallback across providers
- CachingLLMProvider: caching wrapper
- RetryingLLMProvider: retry wrapper

Spec Building:
- DefaultSpecBuilder: basic spec generation
- CronSpecBuilder: cron workflow specialization
- SpecBuilderFactory: builder selection
- CompositeSpecBuilder: multi-strategy fallback
- BuildMetadata: context for builders

Validators:
- StateGraphValidator: DAG structure
- ActivityAvailabilityValidator: activity existence
- TimeoutValidator: timeout format
- CompositeValidator: multiple validators
- TransitionValidator: state transitions

Refactored Components:
- LLMRouter: config-driven, provider-agnostic
- LLMClient: now implements LLMProvider
- llm_router.go: 97 fewer lines (delegated to builders)

Migration Path:
OLD: NewLLMRouter(kb)
NEW: NewLLMRouter(LLMRouterConfig{Provider: ..., KB: ...})

k8s/git-commit.yaml

@@ -9,6 +9,6 @@ metadata:
     app.kubernetes.io/name: poimen
     app.kubernetes.io/component: orchestrator
 data:
-  GIT_COMMIT: "b37319a9"  # Updated automatically by CI/CD
+  GIT_COMMIT: "ca0a9376"  # Updated automatically by CI/CD
   GIT_BRANCH: "main"
   DEPLOYMENT_DATE: "2026-09-03"

k8s/worker-deployment.yaml

@@ -13,7 +13,7 @@ spec:
       labels:
         app: poimen-worker
       annotations:
-        git-commit: "b37319a9"  # ✅ Updated on each push, triggers rolling restart
+        git-commit: "ca0a9376"  # ✅ Updated on each push, triggers rolling restart
         deployment-date: "2026-09-03"
     spec:
       containers: