A column can be empty, as acme's can; new panes go where acme's makenewwindow puts them

Newcol makes an empty column; closing a column's last pane leaves it empty with
the keyboard on its tag; Delcol and Joincol alone take a column away; the
session's last pane closing quits. The +New stand-in and replaceStillborn /
stillborn_joiner are gone. Every new pane goes through exec.placeNew, which
follows acme's makenewwindow (active column, empty column whole, blank space,
halving the biggest) or, with Placement pardes, the old rules. ColumnTags is
gone: column tags are always shown. A grip drag shows acme's box cursor.

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

1 files changed, 5 insertions, 3 deletions

diff --git a/test/snapshots/layout-close.snap b/test/snapshots/layout-close.snap
index 4ae3e31f..b168eb2b 100644
--- a/test/snapshots/layout-close.snap
+++ b/test/snapshots/layout-close.snap
@@ -1,7 +1,9 @@
 # every pane close hands its space to ONE sibling, the rest of the column
 # keeps its sizes: Alt-c move-out, tag Del, and shell exit (pty EOF); an
-# emptied column hands its width to one neighbor
+# emptied column stays, as acme's does, its tag over blank space
 file marker.txt x
+# its clicks and goldens were laid out by the pardes placement rule
+config Placement pardes
 start 41 140 -n 3
 wait 8000 marker.txt
 stable 700 20000
@@ -49,8 +51,8 @@ text exit
 key enter
 stable 700 10000
 snap exit
-# exit the moved-out pane's shell: its column empties and returns its width to
-# the source column it was carved from; the untouched right column stays put
+# exit the moved-out pane's shell: its column stays where it was, empty, the
+# keyboard on its tag; the other columns keep their widths
 press left 40 9
 release left 40 9
 stable 400 5000