core: free allocated writes in read-only mode (#13574)

Read-only filtering happens in Surface.queueIo after callers construct
the message. This early return leaked write_alloc payloads because the
IO thread never receives them and therefore does not perform its normal
cleanup.

src/Surface.zig

@@ -872,9 +872,13 @@ fn queueIo(
         switch (msg) {
             .write_small,
             .write_stable,
-            .write_alloc,
             => return,
 
+            .write_alloc => |v| {
+                v.alloc.free(v.data);
+                return;
+            },
+
             else => {},
         }
     }
@@ -6064,3 +6068,18 @@ fn presentSurface(self: *Surface) !void {
 pub fn getProcessInfo(self: *Surface, comptime info: ProcessInfo) ?ProcessInfo.Type(info) {
     return self.io.getProcessInfo(info);
 }
+
+test "queueIo frees allocated writes in readonly mode" {
+    const testing = std.testing;
+
+    const surface = try testing.allocator.create(Surface);
+    defer testing.allocator.destroy(surface);
+    surface.readonly = true;
+
+    // queueIo must free allocated writes in read-only mode.
+    const data = try testing.allocator.dupe(u8, "\x1b]lGhostty\x1b\\");
+    surface.queueIo(.{ .write_alloc = .{
+        .alloc = testing.allocator,
+        .data = data,
+    } }, .unlocked);
+}