A desktop session holds 64 panes, and every route that finds none free says so

Sixteen panes was far too few for a real session. MAX_PANES is now 64 on a
desktop and stays 16 on the board; the 48 more slots cost about 3.7 KB each
in fixed tables (the core 1.33 to 1.45 MB, its surface 19 to 72 KB), and a
pane itself (84 KB and its terminal) is allocated only when it opens. At the
cap, pane/new fails with `pane/new: no pane slots: 64 max` and an err
record rather than a bare ENFILE, a 9P look or exec that would open a pane
fails its write with the same words and reads back empty, and New, Tty,
Tutor and Alt-n say it on the message row (their ctl writes fail with it).

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

1 files changed, 1 insertions, 1 deletions

diff --git a/src/builtins.zig b/src/builtins.zig
index 5b1b4dcb..32e3cd84 100644
--- a/src/builtins.zig
+++ b/src/builtins.zig
@@ -1102,7 +1102,7 @@ pub const Joincol = struct {
 pub const Tutor = struct {
     pub const scope: Scope = .session;
     pub fn run(c: Ctx) void {
-        const free = c.p.freeSlot() orelse return;
+        const free = c.p.freeSlot() orelse return c.p.reportError(c.id, "Tutor", error.NoPaneSlots);
         _ = c.p.openTutorView(free) catch return;
         exec.placeNew(c.p, c.id, c.id, free, .doc); // a doc like any other
     }