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, 3 insertions, 3 deletions

diff --git a/docs/cloud9.md b/docs/cloud9.md
index 8d4b6b44..7365bf65 100644
--- a/docs/cloud9.md
+++ b/docs/cloud9.md
@@ -23,9 +23,9 @@ is parked with `Status.again` -- the engine parks reads, writes, opens,
 truncations, clunks and removes -- and retried by `Runner.wakeAll` when the
 editor next rests. A read with nothing yet parks the same way, but is never
 retried for news: the core holds it (`ctlfs.hold`) and `answerHeld` answers
-it on its connection through `Conn.reply`'s engine, under the connection's
-lock and only while the engine still holds that tag parked, since cloud9 does
-not tell the backend about a Tflush. `src/9p_quic.zig` selects the existing `pardes-9p` ALPN for
+it through the ticket `Conn.hold` gave its park, with `Conn.answerWith`,
+which makes the answer only while that very park still waits (not flushed,
+its fid not clunked, not out being retried) and under the same lock. `src/9p_quic.zig` selects the existing `pardes-9p` ALPN for
 cloud9's optional OpenSSL transport; QUIC still runs on the poll loop in
 `src/9p_io.zig` on the editor's thread, since cloud9's QUIC adapter is
 nonblocking-descriptor based rather than `std.Io` based.