Split control messages by scope: the root ctl takes the session's builtins and reads the settings, a pane's ctl its own

Every builtin could only be clicked, or written to exec, and the settings
could be read only as the Config window's prose. acme keeps window verbs on
a window's ctl, and webfs and upas/fs keep session settings on a root ctl.
Each builtin now declares its scope (scope = .session; settings are all
session, the rest pane), read by the registry. The root /ctl takes session
builtins and reads every setting in the words a write takes, so its read
written back changes nothing (panel and scene effects now take on/off like
the toggles, to make that true); a pane's ctl takes the pane's builtins
beside get, lock and unlock. Writes are checked whole and refused in Plan
9's ctl words (unknown control message "X", wrong #args ...), which 9ns
now maps to EINVAL (cloud9 re-pinned at a8c7a715). A builtin that would
prompt for its argument fails the write instead, and a refusal is answered
at once, not after the frame.

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

1 files changed, 6 insertions, 2 deletions

diff --git a/src/ninep/tree.zig b/src/ninep/tree.zig
index b0de446e..13dfb0cf 100644
--- a/src/ninep/tree.zig
+++ b/src/ninep/tree.zig
@@ -175,6 +175,7 @@ pub const TopFile = enum(u4) {
     pane,
     new,
     focus,
+    ctl,
 
     pub fn fileName(f: TopFile) []const u8 {
         return if (f == .root) "/" else @tagName(f);
@@ -183,7 +184,7 @@ pub const TopFile = enum(u4) {
     pub fn mode(f: TopFile) u16 {
         return switch (f) {
             .root, .pane => 0o755,
-            .look, .exec, .log, .focus => 0o666,
+            .look, .exec, .log, .focus, .ctl => 0o666,
             .README, .index, .status, .screen, .listeners, .new => 0o444,
         };
     }
@@ -445,6 +446,7 @@ fn topSize(p: *Pardes, f: TopFile) u64 {
         .look, .exec => ctl.resultsLen(p),
         .log => events.logLen(&p.fs.log),
         .listeners => screen.listenersLen(p),
+        .ctl => ctl.rootLen(p),
         .focus => focus: {
             const pn = p.panes[p.active] orelse break :focus 0;
             var digits: [16]u8 = undefined;
@@ -523,7 +525,7 @@ fn readdir(p: *Pardes, req: Req, target: Target) Reply {
                 }
                 if (skip > 0) skip -= 1 else stageDirent(out, p.gpa, fs.os_root, true, "os");
                 // After the first ten, which older clients list by position.
-                inline for (.{TopFile.focus}) |t| {
+                inline for (.{ TopFile.focus, TopFile.ctl }) |t| {
                     if (skip > 0) skip -= 1 else stageDirent(out, p.gpa, @intFromEnum(t), t.dir(), t.fileName());
                 }
                 sources.stage(p, out, "", &skip);
@@ -716,6 +718,7 @@ fn read(p: *Pardes, req: Req, target: Target) Reply {
             .screen => screen.readSnapshot(p, req, null),
             .listeners => screen.readListeners(p, req),
             .focus => ctl.readFocus(p, req),
+            .ctl => ctl.readRoot(p, req),
             // The serial the open handed this fid, so that two reads of one
             // fid answer the same pane: the read observes, the open acted.
             .new => serial: {
@@ -749,6 +752,7 @@ fn write(p: *Pardes, req: Req, target: Target) Reply {
             .look, .exec => ctl.command(p, req, null, f == .exec),
             .log => events.writeLog(p, req),
             .focus => ctl.writeFocus(p, req),
+            .ctl => ctl.writeRoot(p, req),
             else => Reply.fail(req.tag, E.PERM),
         },
         .pane => |t| {