feat(rename): prompt RENAME step by step instead of requiring all args

Bare RENAME printed a usage line and did nothing; only the fully-typed
`RENAME <type> <old> <new>` form worked. Add a stepped front-end
(RenameCommand) that prompts for the object type — as clickable buttons
(Layer, Text style, Dim style, Linetype, UCS, View) — then the current
name, then the new name, and dispatches to the existing inline handler.
The rename logic stays in one place; the argument form is kept and is also
the front-end's dispatch target. BLOCK is left off the buttons because the
inline handler does not implement it.

src/app/commands/styleprops.rs

@@ -1372,7 +1372,16 @@ impl OpenCADStudio {
             }
 
             // ── RENAME table entries ──────────────────────────────────────
-            cmd if cmd == "RENAME" || cmd.starts_with("RENAME ") => {
+            // Bare RENAME prompts step by step (type → old → new); the argument
+            // form below both handles a fully-typed line and is the target the
+            // stepped front-end dispatches to.
+            "RENAME" => {
+                use crate::command::RenameCommand;
+                let c = RenameCommand::new();
+                self.command_line.push_info(&c.prompt());
+                self.tabs[i].active_cmd = Some(Box::new(c));
+            }
+            cmd if cmd.starts_with("RENAME ") => {
                 // Usage: RENAME <type> <old_name> <new_name>
                 // Types: LAYER BLOCK STYLE DIMSTYLE LINETYPE UCS VIEW
                 let parts: Vec<&str> = cmd.split_whitespace().collect();