feat(routing): implement WorkflowSpec validator

Task 1.4 COMPLETE ✅

Comprehensive validation system for workflow specifications:

- validator.go: Main validator with methods:
  - NewValidator(kb) - Create validator with knowledge base
  - ValidateWorkflowSpec(spec) - Validate one-time workflows
  - ValidateCronWorkflowSpec(spec) - Validate scheduled workflows
  - validateState(state, path) - Validate individual states
  - validateDuration(dur) - Validate Go duration strings

- validator_cron.go: Cron expression validation:
  - validateCronExpression(expr) - 5-field cron validation
  - validateCronField(field, min, max, name) - Individual field validation
  - Supports: wildcards (*), ranges (0-59), steps (*/5), lists (0,15,30,45)

- validator_test.go: 30 comprehensive tests
  - Valid/invalid workflow specs
  - State name validation (duplicates, missing)
  - State transitions (Next field references)
  - Catch clause validation
  - Task state validation (activity exists in KB)
  - Pass/Fail state validation
  - Timeout format validation
  - Cron workflow validation
  - Timezone validation
  - Cron expression validation
  - All tests PASS ✅ (39/39 total in routing package)

Acceptance criteria met:
✅ Detects invalid workflow specs
✅ Validates state references and transitions
✅ Checks activities exist in knowledge base
✅ Validates timeout durations
✅ Validates cron expressions
✅ Validates timezones
✅ All validation tests pass
✅ Ready for Phase 2 (llm-router)

Effort: 3 hours (estimated)
Files: validator.go (281 lines)
       validator_cron.go (50 lines)
       validator_test.go (367 lines)

Phase 1 COMPLETE ✅
- Task 1.1: Types ✅
- Task 1.2: Knowledge Base ✅
- Task 1.3: KB Loader ✅
- Task 1.4: Validator ✅

Total Phase 1 Effort: 10 hours (on track with 8-10 estimate)

k8s/git-commit.yaml

@@ -9,6 +9,6 @@ metadata:
     app.kubernetes.io/name: poimen
     app.kubernetes.io/component: orchestrator
 data:
-  GIT_COMMIT: "f03184ad"  # Updated automatically by CI/CD
+  GIT_COMMIT: "b17def78"  # Updated automatically by CI/CD
   GIT_BRANCH: "main"
   DEPLOYMENT_DATE: "2026-08-31"