Insert Ctrl-s commits an undo checkpoint mid-session

helix commit_undo_checkpoint: u after the insert session goes back to the
text as it was at Ctrl-s, a second u to before the session. It pushes an
undo snapshot where the session stands.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 4 insertions, 0 deletions

diff --git a/test/hxcases/cases.jsonl b/test/hxcases/cases.jsonl
index f23a8b2f..15e53590 100644
--- a/test/hxcases/cases.jsonl
+++ b/test/hxcases/cases.jsonl
@@ -448,6 +448,10 @@
 {"name": "goto-last-mod-select", "pane": "file", "text": "ab\ncd\nef\n", "keys": "jjiX<esc>ggvg."}
 {"name": "alt-u-undo", "pane": "file", "text": "ab\n", "keys": "iX<esc><A-u>"}
 {"name": "alt-U-redo", "pane": "file", "text": "ab\n", "keys": "iX<esc>u<A-U>"}
+{"name": "ins-checkpoint-undo", "pane": "file", "text": "ab\n", "keys": "iX<C-s>Y<esc>u"}
+{"name": "ins-checkpoint-undo-twice", "pane": "file", "text": "ab\n", "keys": "iX<C-s>Y<esc>uu"}
+{"name": "ins-checkpoint-redo", "pane": "file", "text": "ab\n", "keys": "iX<C-s>Y<esc>uuU"}
+{"name": "msel-ins-checkpoint", "pane": "file", "text": "ab\nab\n", "keys": "CiX<C-s>Y<esc>u"}
 {"name": "msel-align-basic", "pane": "file", "text": "a=1\nbbb=2\n", "keys": "%s=<ret>&"}
 {"name": "msel-align-columns", "pane": "file", "text": "a,b,c\nccc,d,e\n", "keys": "%s,<ret>&"}
 {"name": "msel-align-uneven", "pane": "file", "text": "a,b\nccc,d,eee,f\n", "keys": "%s,<ret>&"}