Feat: DIST / ID / AREA inquiry commands

Add three classic CAD measurement commands:
- DIST (DI): two-point pick → distance, angle, delta XYZ
- ID: one-point pick → coordinates
- AREA: multi-point polygon pick (Enter to close) → area + perimeter

New CmdResult::Measurement(String) variant ends active command and
prints result to command line without modifying the document.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/modules/home/mod.rs

@@ -5,6 +5,7 @@ pub mod defaults;
 mod donate;
 pub mod draw;
 pub mod groups;
+pub mod inquiry;
 pub mod layers;
 pub mod modify;
 pub mod properties;