layout: every pane open/close resizes exactly ONE sibling — never the whole column. Buggy paths fixed: Alt-n inserted a weight-1 shell (whole column reflowed) — now splitBelow the active pane; stackDocLeft (file/image/tutor open with no doc yet) gave the doc a fair share (every pane shrank) — now it halves only the old top pane's slot; ttyForDir (execute from a file pane) appended a weight-1 shell to the rightmost column — now splitBelow its bottom pane; Alt-c moved a pane out without absorbVWeight (all old siblings grew) — now the sibling above absorbs first. Underneath: splitBelow/absorbVWeight/stackDocLeft snap the whole column's weights to on-screen row counts, because computeGeom's per-pane round(avail*w/vsum) let fractional weights jiggle bystanders by a row; evictLonePristineTty recomputes geometry first (a just-stacked doc has no rect). New snap tests layout-open + layout-close cover Alt-n, doc stacking, ttyForDir, Alt-c, tag Del, pty EOF, and column-width handoff. Six goldens regenerated (fileedit, images, look-file, syntax, tutor, windowops): they had frozen the fair-share/append reflow this change removes; every diff is only the doc/split pane sizing, with untouched panes' boundaries restored bit-identical (e.g. bottom pane tag back at its boot row 17 instead of pushed to 22).

1 files changed, 155 insertions, 0 deletions

diff --git a/test/snapshots/layout-open.golden b/test/snapshots/layout-open.golden
new file mode 100644
index 00000000..2da61d61
--- /dev/null
+++ b/test/snapshots/layout-open.golden
@@ -0,0 +1,155 @@
+== snap before grid=100x30 cursor=4,7
+|Kill Newcol Tutor Debug Colors NextColor Dump
+|  nm /tmp/pardes-snap/layout-open/cwd Del           nm /tmp/pardes-snap/layout-open/cwd Del
+|
+|  sub                                               sub
+|
+|
+|
+|    echo one; echo two
+|
+|
+|
+|
+|
+|
+|
+|
+|  nm /tmp/pardes-snap/layout-open/cwd Del
+|
+|  sub
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+== snap altn-left grid=100x30 cursor=4,8
+|Kill Newcol Tutor Debug Colors NextColor Dump
+|  nm /tmp/pardes-snap/layout-open/cwd Del           nm /tmp/pardes-snap/layout-open/cwd Del
+|
+|  sub                                               sub
+|
+|  nm /tmp/pardes-snap/layout-open/cwd Del
+|
+|  sub
+|
+|
+|
+|
+|
+|
+|
+|
+|  nm /tmp/pardes-snap/layout-open/cwd Del
+|
+|  sub
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+== snap altn-right grid=100x30 cursor=54,8
+|Kill Newcol Tutor Debug Colors NextColor Dump
+|  nm /tmp/pardes-snap/layout-open/cwd Del           nm /tmp/pardes-snap/layout-open/cwd Del
+|
+|  sub                                               sub
+|
+|  nm /tmp/pardes-snap/layout-open/cwd Del           nm /tmp/pardes-snap/layout-open/cwd Del
+|
+|  sub                                               sub
+|
+|
+|
+|
+|
+|
+|
+|
+|  nm /tmp/pardes-snap/layout-open/cwd Del
+|
+|  sub
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+|
+== snap file-open grid=100x30 cursor=7,2
+|Kill Newcol Tutor Debug Colors NextColor Dump
+|  nm /tmp/pardes-snap/layout-open/cwd/sub/f.txt Sa  nm /tmp/pardes-snap/layout-open/cwd Del
+|     1 echo 'TTY'OK
+|  nm /tmp/pardes-snap/layout-open/cwd Del           sub
+|
+|  nm /tmp/pardes-snap/layout-open/cwd Del           nm /tmp/pardes-snap/layout-open/cwd Del
+|
+|  sub                                               sub
+|
+|
+|
+|
+|
+|
+|
+|
+|  nm /tmp/pardes-snap/layout-open/cwd Del
+|
+|  sub
+|
+|
+|
+|
+|
+|
+|
+|    sub/f.txt
+|
+|
+|
+== snap ttydir grid=100x30 cursor=7,2
+|Kill Newcol Tutor Debug Colors NextColor Dump
+|  nm /tmp/pardes-snap/layout-open/cwd/sub/f.txt Sa  nm /tmp/pardes-snap/layout-open/cwd Del
+|     1 echo 'TTY'OK
+|  nm /tmp/pardes-snap/layout-open/cwd Del           sub
+|
+|  nm /tmp/pardes-snap/layout-open/cwd Del           nm /tmp/pardes-snap/layout-open/cwd Del
+|
+|  sub                                               sub
+|
+|                                                    nm /tmp/pardes-snap/layout-open/cwd/sub Del
+|                                                    echo 'TTY'OK
+|
+|                                                    TTYOK
+|
+|
+|
+|  nm /tmp/pardes-snap/layout-open/cwd Del
+|
+|  sub
+|
+|
+|
+|
+|
+|
+|
+|    sub/f.txt
+|
+|
+|