docs(worker): correct tier from 2 to 3 and fix dependency tier refs

worker depends on launcher (now correctly Tier 2) and logz (Tier 1),
placing it at Tier 3. The previous docs cited launcher as Tier 1 and
logz as Tier 0, both of which were wrong.

compliance_test.go

@@ -0,0 +1,8 @@
+package worker_test
+
+import (
+	"code.nochebuena.dev/go/logz"
+	"code.nochebuena.dev/go/worker"
+)
+
+var _ worker.Component = worker.New(logz.New(logz.Options{}), worker.Config{})