Feat: DIVIDE and MEASURE commands — place points along entities

DIVIDE (DIV): entity pick → type N → places N-1 Point entities at equal spacing.
MEASURE (ME): entity pick → type distance → places points at fixed intervals.

Supported entities: Line, Arc, Circle, LwPolyline.
Uses CmdResult::DivideEntity / MeasureEntity with geometry computed in cmd_result.

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

src/command/mod.rs

@@ -99,6 +99,10 @@ pub enum CmdResult {
     BreakEntity { handle: Handle, p1: Vec3, p2: Vec3 },
     /// Attempt to join the given entities into fewer merged entities.
     JoinEntities(Vec<Handle>),
+    /// Place Point entities at N equal intervals along the entity.
+    DivideEntity { handle: Handle, n: usize },
+    /// Place Point entities at `segment_length` intervals along the entity.
+    MeasureEntity { handle: Handle, segment_length: f64 },
 }
 
 // ── Trait ─────────────────────────────────────────────────────────────────