Run bg-transform callbacks during wait instead of dropping them

Wait-block guard returned early for all actions but abort/cancel,
silently discarding actAsync so bg-transform results completing mid-wait
were lost. Let actAsync through since it's unrelated to the wait.

src/terminal.go

@@ -6747,8 +6747,11 @@ func (t *Terminal) Loop() error {
 					callback(a.a)
 				}
 			}
-			// When wait-blocked, only allow abort/cancel
-			if t.waitBlocked {
+			// When wait-blocked, only allow abort/cancel. Background transform
+			// callbacks (actAsync) are let through since they're unrelated to the
+			// wait; blocking them would silently drop bg-transform results that
+			// complete while waiting.
+			if t.waitBlocked && a.t != actAsync {
 				if a.t == actAbort || a.t == actCancel {
 					t.unblockWait()
 					t.pendingActions = nil

test/test_core.rb

@@ -1185,6 +1185,15 @@ class TestCore < TestInteractive
     tmux.until { |lines| assert_equal 1, lines.match_count }
   end
 
+  def test_wait_action_bg_transform
+    # A bg-transform result is unrelated to the wait, so it's applied while the
+    # wait is still blocking rather than dropped. The long read keeps the wait
+    # blocked so the (instant) bg-transform completes during the block; the
+    # header must show while '(..)' is still displayed.
+    tmux.send_keys %((seq 100; sleep 2) | #{FZF} --bind 'start:bg-transform-header(echo hello)+search(5)+wait'), :Enter
+    tmux.until { |lines| assert(lines.any_include?('(..)') && lines.any_include?('hello')) }
+  end
+
   def test_clear_selection
     tmux.send_keys %(seq 100 | #{FZF} --multi --bind space:clear-selection), :Enter
     tmux.until { |lines| assert_equal 100, lines.match_count }