feat(commands): integrate standard CAD commands and fix behavior gaps

Broad pass over the command set: integrate missing commands, wire
previously-unreachable ribbon/menu buttons, and correct name/behaviour
mismatches. Every UI command token now resolves (real handler where the
infrastructure exists, an honest "not yet implemented" status otherwise).

New commands:
- Draw: 3DPOLY, 2D solid (SO/SOLID2D), HELIX, TRACE, SKETCH, DIMCENTER
  (DCE/CENTERMARK)
- Modify/inquiry: REVERSE, MEASUREGEOM (MEA), DBLIST
- Data/manage: BASE, OVERKILL (exact-duplicate removal), AUDIT (read-only
  integrity report), SETVAR (system-variable get/set), SCRIPT (.scr runner),
  FINDNONPURGEABLE

Behaviour fixes:
- LINE and SPLINE gain Close/Undo; AREA computes area/perimeter in f64
  (correct at large coordinates)
- ATTEDIT/ATE unified so the alias and the ribbon button open the
  interactive editor; -ATTEDIT is the command-line form
- Linear/aligned/radius/diameter dimensions gain a text override (Text) and
  text angle (Angle) option
- INSERT gains Scale/Rotate options; COPY gains an Array option
- LINETYPE SET sets the current entity linetype; SETBYLAYER resets overrides
- UNDO accepts a step count

Integrations: standard dimension/block aliases (DLI/DRA/DAN, BMAKE,
EXPORTPDF, DDIM), drafting-aid and screen toggles (GRID/SNAP/POLAR/OSNAP/
DSETTINGS/CLEANSCREEN/QUICKPROPERTIES), viewport tiling
(CASCADE/HORIZONTAL/VERTICAL/VPJOIN), and customization entry points
(CUI/ALIASEDIT).

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

src/modules/insert/base_point.rs

@@ -1,4 +1,7 @@
+use crate::command::{CadCommand, CmdResult};
 use crate::modules::{IconKind, ModuleEvent, ToolDef};
+use glam::DVec3;
+
 pub const ICON: IconKind = IconKind::Svg(include_bytes!("../../../assets/icons/base_point.svg"));
 pub fn tool() -> ToolDef {
     ToolDef {
@@ -8,3 +11,35 @@ pub fn tool() -> ToolDef {
         event: ModuleEvent::Command("BASE".to_string()),
     }
 }
+
+// ── Command implementation ────────────────────────────────────────────────
+
+/// Picks one point and delegates to the inline `BASE <x> <y> <z>` handler,
+/// which writes the active space's insertion base point onto the document.
+pub struct BaseCommand;
+
+impl BaseCommand {
+    pub fn new() -> Self {
+        Self
+    }
+}
+
+impl CadCommand for BaseCommand {
+    fn name(&self) -> &'static str {
+        "BASE"
+    }
+
+    fn prompt(&self) -> String {
+        "BASE  Specify base point:".to_string()
+    }
+
+    fn on_point(&mut self, pt: DVec3) -> CmdResult {
+        CmdResult::Dispatch(format!("BASE {} {} {}", pt.x, pt.y, pt.z))
+    }
+
+    fn on_enter(&mut self) -> CmdResult {
+        CmdResult::Cancel
+    }
+}
+
+inventory::submit!(crate::command::CommandRegistration { names: &["BASE"] }); // BaseCommand