New and Tty run at /tagexec and a column's exec, and with no pane at all

The words New and Tty make a pane in the session's directory, and fs.md
already has them run at a tag no pane owns. But /tagexec refused New as a
pane's word, since the workspace tag does not hold it. Every header exec
also failed ENOENT when no pane was left, and Tty gave up when it had no
pane to take a directory from. Now New and Tty are every tag's words.
A header exec with no pane runs at the stand-in, as a click in the empty
window's tag does, and Tty with no pane asking starts in the session's
directory, as New's scratch does.

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

1 files changed, 2 insertions, 1 deletions

diff --git a/src/exec.zig b/src/exec.zig
index 8c062f66..5b0b0250 100644
--- a/src/exec.zig
+++ b/src/exec.zig
@@ -346,7 +346,8 @@ pub fn spawnV9fsTty(p: *Pardes, from: usize) void {
 }
 
 fn spawnTtyWithMount(p: *Pardes, from: usize, v9fs: bool) ?*Pane {
-    if (p.panes[from] == null) return null;
+    // No pane asking (an empty window's tag): the session's directory, as
+    // New's scratch is.
     // A directory that is not there makes no terminal: its shell could not
     // start in it, and a dead pane would answer no run. Asked only of a host
     // that starts shells (none, as in the core's tests, starts none).