fix(tests): add delay after send_keys in waiter test

Fixes test_wait_for_pane_content_exact_match_detailed failure on tmux 3.1b
where capture_pane() was called immediately after send_keys() before the
content had been flushed/rendered by tmux.

The race condition manifested as:
  AssertionError: assert 'UNIQUE_TEST_STRING_123' in ''

Adding a 0.1s delay after send_keys() allows tmux to flush the content
before capture_pane() is called, fixing the timing issue on older versions.

Author: tony

tests/_internal/test_waiter.py

@@ -1847,6 +1847,9 @@ def test_wait_for_pane_content_exact_match_detailed(wait_pane: Pane) -> None:
     # Send a unique string that we can test with an exact match
     wait_pane.send_keys("UNIQUE_TEST_STRING_123", literal=True)
 
+    # Small delay to allow tmux to flush content (needed for older versions like 3.1b)
+    time.sleep(0.1)
+
     # Get the current content to work with
     content = wait_pane.capture_pane()
     content_str = "\n".join(content if isinstance(content, list) else [content])