Tty in a missing directory fails and makes no pane; a shell that never started answers runs

The host could not start the shell (its chdir failed), and the pane stayed
with no pty: a run written to it waited for a prompt for ever. Tty now
refuses a directory that is not there, `Tty: <dir>: no such directory`,
before making a pane; and a terminal whose shell the host could not start
(Pardes.shellFailed, from each host's spawn) answers any run with
`error shell gone`.

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

1 files changed, 4 insertions, 2 deletions

diff --git a/docs/fs.md b/docs/fs.md
index cfcb62a3..7470bdf3 100644
--- a/docs/fs.md
+++ b/docs/fs.md
@@ -885,8 +885,10 @@ carries no reason or code, and the shell's own complaint is in the pane's
 body (`tail body`); `exit N` and what it printed when the line ended the shell
 itself (`exit 3`, or `echo bye; exit 3`): its terminal closes, and a read
 of the run's open still answers after the pane is gone; `error shell gone`
-when the pane closed or its shell was replaced, or the shell went without
-an exit status to tell; `error no prompt marks` for a shell pardes could not instrument;
+when the pane closed or its shell was replaced, the shell went without
+an exit status to tell, or it never started (a `Tty` in a directory that is
+not there is refused before, `Tty: <dir>: no such directory`, and makes no
+pane); `error no prompt marks` for a shell pardes could not instrument;
 `error command done; not a shell` (or `error a command runs here, not a
 shell`) on a command pane, whose child is its command.
 It relies on the OSC 133 marks pardes injects into bash and fish, tagged