Use worker.WorkerDeploymentVersion struct instead of string concatenation

Replace string concatenation for the Version field with the proper
worker.WorkerDeploymentVersion struct that has separate DeploymentName
and BuildId fields. This follows the Temporal SDK's expected API.

Addresses: #130 (comment)

Author: jlegrone

go.work

@@ -4,5 +4,6 @@ toolchain go1.24.6
 
 use (
 	.
+	./internal/demo
 	./internal/tests
 )

internal/demo/util/worker.go

@@ -32,8 +32,11 @@ func NewVersionedWorker(opts worker.Options) (w worker.Worker, stopFunc func())
 	}()
 
 	opts.DeploymentOptions = worker.DeploymentOptions{
-		UseVersioning:             true,
-		Version:                   mustGetEnv("TEMPORAL_DEPLOYMENT_NAME") + VersionIDSeparator + mustGetEnv("TEMPORAL_WORKER_BUILD_ID"),
+		UseVersioning: true,
+		Version: worker.WorkerDeploymentVersion{
+			DeploymentName: mustGetEnv("TEMPORAL_DEPLOYMENT_NAME"),
+			BuildId:        mustGetEnv("TEMPORAL_WORKER_BUILD_ID"),
+		},
 		DefaultVersioningBehavior: workflow.VersioningBehaviorPinned,
 	}