Fold newsletter compose into Subscribers as a second feature, not its own alternative

Per feedback: sending a newsletter is naturally part of "Subscribers",
not a separate review task. Also fixes a real bug - the standalone
Compose newsletter alternative had no `action`, so AlternativeCard
never rendered a submit button/form for it at all (has_action gates
the <form>, unconditionally). action: /review reloads the dashboard
after sending.

questions/review.yaml

@@ -33,21 +33,18 @@ alternatives:
 
   - name: Subscribers
     description: ""
+    action: /review
+    consequence: [Send]
     features:
       - name: ""
         description: ""
         resource:
           bucket: portal_subscribers
           requires_group: owners
-
-  - name: Compose newsletter
-    description: >
-      Sends to everyone in Subscribers - picked up by an automation
-      watching this question, not portal itself.
-    consequence: [Send]
-    features:
-      - name: ""
-        description: ""
+      - name: Compose newsletter
+        description: >
+          Sends to everyone above - picked up by an automation watching
+          this question, not portal itself.
         requirements:
           - name: subject
             label: Subject