fix: open-issue sweep — drawing, plot, snap, layout and UI fixes

Fixes:
- Font prompt no longer lists bundled ltypeshp/qcadshp shape files (#1626)
- Wide polylines step at a discontinuous segment width; PEDIT marks the
  current vertex; keyword steps refresh the command preview (#1628)
- Radius-0 fillet drops the zero-length segment it left, so the corner
  fillets again (#1422)
- FILLET Trim / No trim option (#1558)
- True-colour wires plot in their own colour; colour picker stores the
  value it shows (#1621)
- Model tab keeps its page setup; "Save changes to layout" in Model (#1620)
- QNEW default template in Options > Files; .dwt in the open dialog
  (#1134, #1113)
- GRIDUNIT / GRIDMODE / PERSPECTIVE variables (#1618, #1524)
- PTYPE (#1433)
- ZOOM nX / nXP (#1465)
- CHSPACE between model and paper space through a viewport (#1428)
- Moving a dimension keeps its automatic text placement
- Shell icon; "&&" button labels (#1554)
- LINETYPE Load from a .lin file (#1588)
- XLINE / RAY hide the crosshair arms (#1437)
- Dynamic-input boxes keep clear of the crosshair and each other (#1546)
- Snap marker colour setting, dark default on light canvases
  (#1497, #1229, #1128)
- Dimension style precision as a 0.00 pattern dropdown (#1426)
- Node graph nodes left of the origin no longer clip away (#1592)
- Collapse button in the command history header (#1094)
- Freeze-in-current-viewport toggle in the ribbon layer list (#1466)
- Geometric Center object snap for closed polylines (#1369)

New strings translated in all 21 locales.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/ui/icons.rs

@@ -32,6 +32,8 @@ static REDO: &[u8] = include_bytes!("../../assets/icons/ui/redo.svg");
 static OSNAP_ENDPOINT: &[u8] = include_bytes!("../../assets/icons/osnap/endpoint.svg");
 static OSNAP_MIDPOINT: &[u8] = include_bytes!("../../assets/icons/osnap/midpoint.svg");
 static OSNAP_CENTER: &[u8] = include_bytes!("../../assets/icons/osnap/center.svg");
+static OSNAP_GEOMETRIC_CENTER: &[u8] =
+    include_bytes!("../../assets/icons/osnap/geometric_center.svg");
 static OSNAP_NODE: &[u8] = include_bytes!("../../assets/icons/osnap/node.svg");
 static OSNAP_QUADRANT: &[u8] = include_bytes!("../../assets/icons/osnap/quadrant.svg");
 static OSNAP_INTERSECTION: &[u8] = include_bytes!("../../assets/icons/osnap/intersection.svg");
@@ -51,6 +53,8 @@ static LAY_ON: &[u8] = include_bytes!("../../assets/icons/layers/layon.svg");
 static LAY_OFF: &[u8] = include_bytes!("../../assets/icons/layers/layoff.svg");
 static LAY_FRZ: &[u8] = include_bytes!("../../assets/icons/layers/layfrz.svg");
 static LAY_THW: &[u8] = include_bytes!("../../assets/icons/layers/laythw.svg");
+static LAY_VP_FRZ: &[u8] = include_bytes!("../../assets/icons/layers/layvpfrz.svg");
+static LAY_VP_THW: &[u8] = include_bytes!("../../assets/icons/layers/layvpthw.svg");
 static LAY_LCK: &[u8] = include_bytes!("../../assets/icons/layers/laylck.svg");
 static LAY_ULK: &[u8] = include_bytes!("../../assets/icons/layers/layulk.svg");
 
@@ -630,6 +634,7 @@ pub fn osnap(snap: crate::snap::SnapType) -> &'static [u8] {
         S::Endpoint => OSNAP_ENDPOINT,
         S::Midpoint => OSNAP_MIDPOINT,
         S::Center => OSNAP_CENTER,
+        S::GeometricCenter => OSNAP_GEOMETRIC_CENTER,
         S::Node => OSNAP_NODE,
         S::Quadrant => OSNAP_QUADRANT,
         S::Intersection => OSNAP_INTERSECTION,
@@ -694,6 +699,15 @@ pub fn layer_freeze(frozen: bool) -> &'static [u8] {
     }
 }
 
+/// Freeze-in-current-viewport icon bytes (frozen / thawed).
+pub fn layer_vp_freeze(frozen: bool) -> &'static [u8] {
+    if frozen {
+        LAY_VP_FRZ
+    } else {
+        LAY_VP_THW
+    }
+}
+
 /// Layer lock icon bytes (locked / unlocked).
 pub fn layer_lock(locked: bool) -> &'static [u8] {
     if locked {