`> exec` through a mount no longer hangs the editor, and a close holding a last line is answered at once: the line runs at the editor's next step

A shell's truncating open of exec (or look, ctl, log, pager) sends a
setattr that changes nothing; it waited for the editor to be quiet, and
through a 9ns mount that quiet could never come: 9ns answers nothing else
on the mount while the setattr is out, and the editor's step may be out
reading a pane's file through it. This was the "truncating open of exec
hangs, only in selfmount" mystery. Only a truncate of a pane's file or a
tag waits now.

A close holding a last line with no newline hands it to the editor's step
(tree.runClosedLines, beside fillClosedPagers), as a /pager close does, and
is answered at once; a refusal is the log's err.

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

1 files changed, 3 insertions, 2 deletions

diff --git a/src/9p_io.zig b/src/9p_io.zig
index 57df0c5f..cb345b00 100644
--- a/src/9p_io.zig
+++ b/src/9p_io.zig
@@ -266,7 +266,7 @@ pub const Listener = struct {
         const restores = pardes.turn.restores;
         // Asked first: a release that runs a held line has none after.
         const changes = pardes.ctlfs.changesPane(core, req);
-        const fills = pardes.ctlfs.holdsPage(core, req);
+        const fills = pardes.ctlfs.handsOff(core, req);
         const reply = core.serveFs(req);
         if (req.op == .release and quiet) l.collectOs();
         // A read with nothing yet stays parked in the engine, and the core
@@ -301,7 +301,8 @@ pub const Listener = struct {
         // whole after the wait.
         l.kick();
         // A read that put a /pager open's text in (ctl.fillPager), or a
-        // close that handed it to the editor's step, waits on nothing the
+        // close that handed its text or last line to the editor's step
+        // (ctl.fillClosedPagers, tree.runClosedLines), waits on nothing the
         // editor performs: its answer goes now, while the turn still keeps
         // a read's payload whole. Waiting would hang a close through a
         // mount: 9ns answers nothing else on it while a clunk is out, and