One shared, content-labeled Confirm button per alternative instead of one per row

Each AnswerRow used to carry its own ServerAction<TransitionAnswer> and
its own "Confirm" button - a page with N open rows showed N buttons.
Selecting a transition now just toggles an entry in a shared
pending_transitions map (keyed by feature_name+item_id) owned by
AlternativeCard; one button, labeled from the alternative's own
consequence field (same mechanism Subscribers' "Send" already used),
confirms every selection at once via the new batch transition_answers.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

style/main.css

@@ -548,29 +548,6 @@ textarea:focus {
   gap: 0.6rem;
 }
 
-.answer-confirm {
-  font-family: var(--sans);
-  font-weight: 600;
-  font-size: 0.82rem;
-  color: #0a0a0a;
-  background: var(--accent);
-  border: none;
-  border-radius: 0.5rem;
-  padding: 0.45rem 1rem;
-  cursor: pointer;
-  transition: filter 120ms;
-}
-
-.answer-confirm:hover {
-  filter: brightness(1.08);
-}
-
-.answer-confirm:disabled {
-  opacity: 0.5;
-  cursor: not-allowed;
-  filter: none;
-}
-
 .item-list {
   display: grid;
   gap: 0.8rem;
@@ -657,6 +634,11 @@ textarea:focus {
   background: var(--accent);
 }
 
+.select-option:disabled {
+  opacity: 0.5;
+  cursor: not-allowed;
+}
+
 @media (max-width: 640px) {
   .hero {
     padding: 3rem 1.25rem 2rem;