pane/new takes rows from a pane in another column before refusing ENOSPC, as acme's placement does

A pane/new whose column had no room was refused "no space for a pane in
that column", even with another column holding a tall pane that could
give rows. acme takes rows wherever a window has them before saying
there are none. pane/new now tries the other columns as +Errors already
did: an empty one, else its tallest pane's bottom half, last column
first. It is refused only when no pane anywhere can give the rows.

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

1 files changed, 4 insertions, 1 deletions

diff --git a/docs/fs.md b/docs/fs.md
index 33cfd581..b37511dd 100644
--- a/docs/fs.md
+++ b/docs/fs.md
@@ -367,7 +367,10 @@ answer the same serial. It goes where acme's makenewwindow puts a window
 if empty, else the bottom half of its last pane. A session holds 64 panes
 (`no space for a pane: 64 max`), and every pane keeps its tag and 2 rows
 (`no space for a pane in that column: each keeps its tag and 2 rows`); both
-are ENOSPC, for this open and for a look, exec, `New` or `Tty` alike.
+are ENOSPC, for this open and for a look, exec, `New` or `Tty` alike. A
+`pane/new` whose column is full takes its rows from a pane in another column
+that has them, last column first, as acme does, and is refused only when
+no pane anywhere can give them.
 `rmdir /pane/<n>` closes the pane, unsaved or not.
 
 **`name`** reads the file name (a terminal's directory); a write renames the