Feat: ALIGN command (AL) — align objects using 1 or 2 point pairs

Workflow: select objects → 1st src/dst pair → 2nd src/dst pair (optional) → Enter.
- 1 pair: pure translation (src1 → dst1)
- 2 pairs: translate + rotate in XZ plane; optional uniform scale (Y/N prompt)

Transform applied as 3 sequential scene.transform_entities calls:
translate to origin → scale → rotate → translate to dst1.

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

src/command/mod.rs

@@ -109,6 +109,14 @@ pub enum CmdResult {
         pick_pt: Vec3,
         mode: crate::modules::home::modify::lengthen::LenMode,
     },
+    /// Align selected entities: translate to dst1, rotate by angle_rad, optional scale.
+    AlignSelected {
+        handles: Vec<Handle>,
+        src1: Vec3,
+        dst1: Vec3,
+        angle_rad: f32,
+        scale: f32,
+    },
 }
 
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