fix(FN-7344): keep planner chat empty state at top

packages/dashboard/app/components/TaskPlannerChatTab.css

@@ -72,7 +72,6 @@ Planner Chat expansion should use the same in-view floating affordance as Activi
 
 .task-planner-chat-state,
 .task-planner-chat-empty {
-  margin: auto;
   display: flex;
   align-items: center;
   gap: var(--space-sm);
@@ -80,15 +79,25 @@ Planner Chat expansion should use the same in-view floating affordance as Activi
   text-align: center;
 }
 
+.task-planner-chat-state {
+  margin: auto;
+}
+
 .task-planner-chat-empty {
   position: relative;
   flex-direction: column;
   width: 100%;
   max-width: 42rem;
+  margin: 0 auto auto;
   gap: var(--space-lg);
   padding-top: var(--space-md);
 }
 
+/*
+FNXC:TaskDetailPlannerChat 2026-07-02-00:41:
+An empty Planner Chat transcript should enter at the top of the chat surface instead of auto-centering or inheriting the message auto-scroll-to-bottom behavior. Once real messages exist, message streaming still scrolls to the latest entry.
+*/
+
 .task-planner-chat-empty-copy {
   display: flex;
   flex-direction: column;

packages/dashboard/app/components/TaskPlannerChatTab.tsx

@@ -319,6 +319,10 @@ export function TaskPlannerChatTab({ task, projectId, active, expanded = false,
 
   useEffect(() => {
     if (!transcriptRef.current) return;
+    if (messages.length === 0) {
+      transcriptRef.current.scrollTop = 0;
+      return;
+    }
     transcriptRef.current.scrollTop = transcriptRef.current.scrollHeight;
   }, [messages, composerState]);
 

packages/dashboard/app/components/__tests__/TaskDetailModal.responsive-and-dependencies.test.tsx

@@ -128,6 +128,7 @@ describe("TaskDetailModal", () => {
       expect(modelBlock).toContain("left: 0;");
       expect(modelBlock).toContain("inline-size: calc(var(--space-2xl) - var(--space-xs));");
       expect(modelBlock).not.toContain("text-overflow: ellipsis;");
+      expect(css).toMatch(/\.task-planner-chat-empty\s*\{[^}]*margin:\s*0 auto auto;/);
       expect(composerBlock).toContain("display: flex;");
       expect(composerBlock).toContain("flex-wrap: wrap;");
       expect(composerBlock).toContain("align-items: stretch;");