A command pane's command is over when its process exits, not when its pty closes

A job left in the background (sleep 100 &) held the pty open, so the pane
stayed running and the child a zombie until the job ended; a command that
closed its terminal and ran on got its end of file at once, the host waited
100 ms for an exit, reported exit ? and hung it up. Now each command's child
is watched on a thread (waitid with WNOWAIT, so its pid stays its own until
the host reaps it), and the host tells the core the exit from that: after the
pty's end of file, so the output before the exit is in, or 50 ms after the
exit without one, a job holding the pty. The pty stays open until both, so a
command that let go of its terminal is never hung up by it. All four front
ends; a host that cannot start the watcher reads the exit at end of file as
before. Tests: host_io's for both cases, and cmdexit.snap end to end.

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

1 files changed, 3 insertions, 3 deletions

diff --git a/src/detached/wire.zig b/src/detached/wire.zig
index 94bd7f0b..0854ce3e 100644
--- a/src/detached/wire.zig
+++ b/src/detached/wire.zig
@@ -819,7 +819,7 @@ fn clientTag(msg: ClientMsg) ClientTag {
     return switch (msg) {
         .event => |ev| switch (ev) {
             // Machine-local reports and 9P requests belong to the session owner.
-            .output, .eof, .lsp_resp, .pipe_resp, .file_changed, .tick => unreachable,
+            .output, .eof, .exited, .lsp_resp, .pipe_resp, .file_changed, .tick => unreachable,
             inline else => |_, t| @field(ClientTag, @tagName(t)),
         },
         inline else => |_, t| @field(ClientTag, @tagName(t)),
@@ -946,7 +946,7 @@ pub fn encodeClient(out: []u8, msg: ClientMsg) Error![]const u8 {
             .touch_scroll => |v| try w.putF32(v),
             .pointer_leave => {},
             // See `clientTag`: no tag, so nothing to encode.
-            .output, .eof, .lsp_resp, .pipe_resp, .file_changed, .tick => unreachable,
+            .output, .eof, .exited, .lsp_resp, .pipe_resp, .file_changed, .tick => unreachable,
         },
     }
     try finishMessage(&w, at);
@@ -1076,7 +1076,7 @@ pub fn clientBound(msg: ClientMsg) usize {
             .paste => |b| b.len,
             .command => |line| line.len,
             // See `clientTag`: not on this wire in this direction.
-            .output, .eof, .lsp_resp, .pipe_resp, .file_changed, .tick => unreachable,
+            .output, .eof, .exited, .lsp_resp, .pipe_resp, .file_changed, .tick => unreachable,
         },
     };
 }