Keep a pane's filesystem state on the Pane instead of a slot-indexed table

addr, limit, the event queue and its readers, pty/data's queue, a waiting
run and the /log announcement flag lived in p.fs.panes[slot], reset when
the pane went; a reused slot is how the bug class came in. acme keeps the
same state on its Window (editors/acme/dat.h:226-266), so now Pane.fs
holds it: announced, retired (noteRetire, which still answers a waiting
run and drops the listener count first) and freed with the pane itself.

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

1 files changed, 3 insertions, 3 deletions

diff --git a/src/ninep/tree.zig b/src/ninep/tree.zig
index 3ebea669..f08d20c8 100644
--- a/src/ninep/tree.zig
+++ b/src/ninep/tree.zig
@@ -543,7 +543,7 @@ fn open(p: *Pardes, req: Req, target: Target) Reply {
         .pane => |t| {
             const id = p.paneBySerial(t.serial) orelse return Reply.fail(req.tag, E.NOENT);
             const pn = p.panes[id].?;
-            const pf = &p.fs.panes[id];
+            const pf = &pn.fs;
             if (t.file.inPty() and !pn.isTerminal()) return Reply.fail(req.tag, E.NOENT);
             switch (t.file) {
                 .body => if (pn.isTerminal()) return screen.openSnapshot(p, req, false),
@@ -605,7 +605,7 @@ fn releaseHandle(p: *Pardes, req: Req) Reply {
             if (t.file == .pty_run) return pty.releaseRun(p, req);
             if (t.file != .event and t.file != .pty_data) return .{ .tag = req.tag };
             const id = p.paneBySerial(t.serial) orelse return .{ .tag = req.tag };
-            const pf = &p.fs.panes[id];
+            const pf = &p.panes[id].?.fs;
             if (t.file == .pty_data) {
                 if (req.handle != reader_handle or pf.pty_readers == 0) return .{ .tag = req.tag };
                 pf.pty_readers -= 1;
@@ -626,7 +626,7 @@ fn setattr(p: *Pardes, req: Req, target: Target) Reply {
     if (req.truncate) switch (target) {
         .pane => |t| {
             const id = p.paneBySerial(t.serial) orelse return Reply.fail(req.tag, E.NOENT);
-            if (pane.truncate(p, id, p.panes[id].?, t.file) != .ok) return Reply.fail(req.tag, E.NOMEM);
+            if (pane.truncate(p, p.panes[id].?, t.file) != .ok) return Reply.fail(req.tag, E.NOMEM);
         },
         .top => {},
     };