test: add LLMTestWorkflow for testing LLM inference

- New workflow: LLMTestWorkflow
- Accepts prompt input (e.g., 'say hello')
- Calls LLMInferenceActivity to invoke local LLM
- Registers LLMInferenceActivity and LLMBatchInferenceActivity
- Returns LLM response text

Testing shows:
✅ Worker connects to Temporal successfully
✅ Activities register on startup
✅ Ready for LLM invocation tests

Usage:
  tctl workflow start --type LLMTestWorkflow \
    --task-queue poimen-taskqueue \
    --input '{"prompt":"say hello"}'

cmd/worker/main.go

@@ -53,6 +53,7 @@ func main() {
 	w.RegisterWorkflow(workflow.TestWorkflow)
 	w.RegisterWorkflow(workflow.RoutingWorkflow)
 	w.RegisterWorkflow(workflow.WorkflowGraphQuery)
+	w.RegisterWorkflow(workflow.LLMTestWorkflow)
 
 	// Register all activities
 	w.RegisterActivity(activity.CloneRepoActivity)
@@ -72,6 +73,8 @@ func main() {
 
 	// Routing workflow activities
 	w.RegisterActivity(activity.LLMRouterActivity)
+	w.RegisterActivity(activity.LLMInferenceActivity)
+	w.RegisterActivity(activity.LLMBatchInferenceActivity)
 	w.RegisterActivity(activity.ValidateWorkflowSpecActivity)
 	w.RegisterActivity(activity.ValidateCronWorkflowSpecActivity)