Answer a held read by its cloud9 ticket, refuse a second, and say a pane shut down

The held read is now kept by the Ticket cloud9's Conn.hold() gives its
park and answered through Conn.answerWith(), which makes the answer only
while that very park still waits, instead of walking the engine's slots
by tag; pardes no longer reaches into the engine for it. A second read on
an open whose read is held fails with file in use rather than sitting
parked where nothing answers it, and a read that waits with no open
record to hold it is logged and asserted on. A read on an event or
pty/data open whose pane closed answers acme's "window shut down"
(editors/acme/xfid.c:1005). The pane keeps its run's and its lock's open
handles, checked through openOf on use, not record indices. Docs: lock
from a shell needs a held fd, and a command that clears the screen may
read as cut.

Needs cloud9 zvuqvnzy (cca47d63), which adds Conn.hold, waiting and
answerWith; build.zig.zon still pins 82d8152c until that is pushed and
re-pinned.

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

1 files changed, 1 insertions, 1 deletions

diff --git a/src/fs-help.txt b/src/fs-help.txt
index 302e6538..4eecad41 100644
--- a/src/fs-help.txt
+++ b/src/fs-help.txt
@@ -42,4 +42,4 @@ Pitfalls, one each:
   Truncating tag clears the part you may edit; truncating dot or addr empties it.
   A terminal's body is a history snapshot frozen per open; pty/data is the live stream.
   A failing command is reported in the editor and in log, not as a write error; a bad line fails the write.
-  pane/<n>/ctl: acme's status line; takes get (reload), lock/unlock (a second lock waits for close/unlock).
+  pane/<n>/ctl: acme's status line; takes get (reload), lock/unlock on a held fd (exec 3>ctl; echo lock >&3).