FN-6340: restrict archive action to done tasks

Limits task card archiving UI to completed tasks while preserving coverage for hidden states.

- Render the archive button only when a task is in the done column.
- Update TaskCard tests to assert archive action visibility for done tasks and absence for other live columns.
- Keep the header action placement assertion focused on done task cards.

Files changed:
 packages/dashboard/app/components/TaskCard.tsx     |  2 +-
 .../app/components/__tests__/TaskCard.test.tsx     | 23 +++++++++++++++++-----
 2 files changed, 19 insertions(+), 6 deletions(-)

Fusion-Task-Id: FN-6340

Fusion-Task-Lineage: e1373fd1-5e50-4784-bf04-fa13ef0a08cb

packages/dashboard/app/components/TaskCard.tsx

@@ -2043,7 +2043,7 @@ function TaskCardComponent({
               <Trash2 size={12} />
             </button>
           )}
-          {task.column !== "archived" && onArchiveTask && (
+          {task.column === "done" && onArchiveTask && (
             <button
               className="card-archive-btn"
               onClick={handleArchiveClick}

packages/dashboard/app/components/__tests__/TaskCard.test.tsx

@@ -462,8 +462,8 @@ describe("TaskCard", () => {
     expect(screen.getByLabelText("Archive task")).toBeDefined();
   });
 
-  it.each(["triage", "todo", "in-progress", "in-review", "done"] as const)(
-    "renders archive action for %s tasks",
+  it.each(["triage", "todo", "in-progress", "in-review"] as const)(
+    "hides archive action for %s tasks",
     (column) => {
       render(
         <TaskCard
@@ -474,10 +474,23 @@ describe("TaskCard", () => {
         />,
       );
 
-      expect(screen.getByLabelText("Archive task")).toBeDefined();
+      expect(screen.queryByLabelText("Archive task")).toBeNull();
     },
   );
 
+  it("renders archive action for done tasks", () => {
+    render(
+      <TaskCard
+        task={makeTask({ column: "done" })}
+        onOpenDetail={noop}
+        addToast={noop}
+        onArchiveTask={vi.fn(async () => makeTask({ column: "archived" }))}
+      />,
+    );
+
+    expect(screen.getByLabelText("Archive task")).toBeDefined();
+  });
+
   it("does not render archive action for archived tasks", () => {
     render(
       <TaskCard
@@ -1994,10 +2007,10 @@ describe("TaskCard", () => {
     expect(actionsContainer?.contains(editBtn)).toBe(true);
   });
 
-  it("renders archive button inside card-header-actions for live columns", () => {
+  it("renders archive button inside card-header-actions for done columns", () => {
     const { container } = render(
       <TaskCard 
-        task={makeTask({ column: "todo", size: "L" })} 
+        task={makeTask({ column: "done", size: "L" })} 
         onOpenDetail={noop} 
         addToast={noop}
         onArchiveTask={async () => makeTask()}