Feat: DIMALIGNED (DAL) and DIMDIAMETER (DDI) dimension commands

DIMALIGNED: 3-click flow (p1 → p2 → dim line position) → DimensionAligned.
Rubber-band preview shows extension lines and dim line offset.

DIMDIAMETER: 3-click flow (center → arc point → text position) → DimensionDiameter.
Previews the diameter chord line.

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

src/modules/annotate/mod.rs

@@ -1,6 +1,8 @@
 // Annotate module — dimension and text annotation tools.
 
+pub mod aligned_dim;
 pub mod angular_dim;
+pub mod diameter_dim;
 pub mod leader_cmd;
 pub mod linear_dim;
 pub mod mleader_cmd;