test(tools): Extend test_paste_text retry window to 5 seconds

why: The CI matrix (GitHub Actions runners) timed out the
retry_until(..., 2) for "PASTE_TEST_marker_xyz" in pane capture
across all six tmux matrix cells — the bash shell cold-start on a
fresh pane can take several seconds before it processes the pasted
echo command and renders output. pyproject's pytest-rerunfailures
config reran each failure twice with no change, so this is a
reliable timing issue rather than a transient flake. paste_text
itself is still verified end-to-end (the marker MUST appear); only
the patience budget grew.

what:
- Bump the timeout passed to retry_until from 2 to 5 seconds.
- Add a comment explaining the cold-start rationale so future
  readers don't shave it back down.

Author: tony

tests/test_pane_tools.py

@@ -965,10 +965,12 @@ def test_paste_text(mcp_server: Server, mcp_pane: Pane) -> None:
     )
     assert "pasted" in result.lower()
 
-    # Verify the text appeared in the pane
+    # Verify the text appeared in the pane. Use a generous retry
+    # window: CI runners cold-start the pane's shell and the echo
+    # output can take several seconds to render on the first run.
     retry_until(
         lambda: "PASTE_TEST_marker_xyz" in "\n".join(mcp_pane.capture_pane()),
-        2,
+        5,
         raises=True,
     )