feat(command): ADDSELECTED draws a new object like the selected one (#239)

Take the first selected entity as a template, adopt its general
properties (layer, colour, linetype, lineweight, linetype scale) as the
current defaults, then start the matching draw command so the object
drawn next inherits them.

Supports Point, Line, Circle, Arc, Ellipse, all polylines (PLINE), Text,
MText, Spline, Hatch, Solid, Ray and XLine; other types report that
creation is unsupported. Registered for command-line autocomplete.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/commands/mod.rs

@@ -520,6 +520,8 @@ inventory::submit!(crate::command::CommandRegistration {
         "SELECTALL",
         "SELECTSIMILAR",
         "SELSIM",
+        // Draw a new object of the same type as the selected one. (#239)
+        "ADDSELECTED",
         "SHEETSET",
         "SHORTCUTS",
         "SSM",