Fix: allow destroying "not now" state when closing cards

- Update `Card::Closeable` to destroy associated "not now" state during close.
- Add new tests to verify closure behavior for different column types, including "not now".

app/models/card/closeable.rb

@@ -31,6 +31,7 @@ module Card::Closeable
   def close(user: Current.user)
     unless closed?
       transaction do
+        not_now&.destroy
         create_closure! user: user
         track_event :closed, creator: user
       end

test/models/card/closeable_test.rb

@@ -31,4 +31,32 @@ class Card::CloseableTest < ActiveSupport::TestCase
     assert cards(:shipping).reload.open?
     assert cards(:shipping).events.last.action.card_reopened?
   end
+
+  test "close card from triage column" do
+    card = cards(:logo)
+    assert_equal columns(:writebook_triage), card.column
+
+    card.close
+    assert card.closed?
+  end
+
+  test "close card from active column" do
+    card = cards(:text)
+    assert_equal columns(:writebook_in_progress), card.column
+
+    card.close
+    assert card.closed?
+  end
+
+  test "close card from NOT NOW" do
+    card = cards(:logo)
+
+    card.postpone
+    assert card.postponed?
+    assert card.not_now.present?
+
+    card.close
+    assert card.closed?
+    assert_nil card.reload.not_now
+  end
 end