ATTDEF dialog error band and multi-line editor; ATTDISP sets ATTMODE

Validation messages show in the dialogs, the Default value of a multi-line
definition can be edited in the multi-line text editor, "Specify on-screen"
is kept for the session, ATTDISP sets ATTMODE with the reference prompt
instead of changing the definitions, and Insert > Block gets the Edit
Attribute (Single / Multiple) and attribute display lists.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app/commands/mod.rs

@@ -666,6 +666,9 @@ inventory::submit!(crate::command::CommandRegistration {
         "POINTCLOUDPOINTMAXLEGACY",
         "XCLIPFRAME",
         "WIPEOUTFRAME",
+        "ATTMODE0",
+        "ATTMODE1",
+        "ATTMODE2",
         "FRAMES0",
         "FRAMES1",
         "FRAMES3",