Newcol at the column cap says so, and a desktop session holds 16 columns

Newcol with every column slot taken, or a column too narrow to split,
did nothing and said nothing. It now fails (a ctl write with it) with no
space for a column: 16 max (ENOSPC through 9ns), or that the column is
too narrow. MAX_COLS is 16 on a desktop, 6 on the board; each column
costs about 8 KB of core state (the Pardes struct grows from 1.47 MB to
1.56 MB), most of it its tag's text. fs.md and the skill give the cap.

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

1 files changed, 2 insertions, 1 deletions

diff --git a/docs/fs.md b/docs/fs.md
index ce33ac7c..09738816 100644
--- a/docs/fs.md
+++ b/docs/fs.md
@@ -112,7 +112,8 @@ Existing Plan9port/v9fs clients need a userspace bridge for QUIC.
 /commands    every builtin: word, `arg` if it takes one, `root`, `pane` or `both` (the ctl that takes it:
              Edit is both, at the active pane from the root; a pane's word such as Undo or Msg
              is refused at the root), a setting's values, then ` -- ` and what it does
-/layout      one line per column, left to right: serial index x width current|notcurrent
+/layout      one line per column (16 at most; the board 6; Newcol past that fails,
+             `no space for a column: 16 max`, ENOSPC), left to right: serial index x width current|notcurrent
              (the column with the keyboard now) empty|full pane-serials...; then active
              <serial>: acme's activecol, which the keyboard leaving for another column's
              tag does not move, so the two can differ -- the active column, where