feat(protocol): job messages, protocol version and job model (#7)

internal/master/events/broker.go

@@ -2,7 +2,10 @@
 // open browser streams.
 package events
 
-import "sync"
+import (
+	"strconv"
+	"sync"
+)
 
 // Topic names what changed. Subscribers refetch that part of the UI.
 type Topic string
@@ -11,8 +14,13 @@ type Topic string
 const (
 	Services Topic = "services"
 	Agents   Topic = "agents"
+	Jobs     Topic = "jobs" // a job was created or changed status
 )
 
+// JobTopic is signalled when job id gets new output or changes status. The
+// name avoids ":" so it is safe inside hx-trigger="sse:job-42".
+func JobTopic(id int64) Topic { return Topic("job-" + strconv.FormatInt(id, 10)) }
+
 // Broker is an in-process publish/subscribe hub.
 type Broker struct {
 	mu   sync.Mutex

internal/master/events/broker_test.go

@@ -46,3 +46,7 @@ func TestBroker_SlowSubscriberDoesNotBlockPublish(t *testing.T) {
 		t.Fatal("Publish blocked on a slow subscriber")
 	}
 }
+
+func TestJobTopic(t *testing.T) {
+	assert.Equal(t, Topic("job-42"), JobTopic(42))
+}