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/app/settings.rs

@@ -251,6 +251,7 @@ const SNAP_ORDER: &[SnapType] = &[
     SnapType::Endpoint,
     SnapType::Midpoint,
     SnapType::Center,
+    SnapType::GeometricCenter,
     SnapType::Node,
     SnapType::Quadrant,
     SnapType::Intersection,
@@ -276,6 +277,7 @@ fn snap_bit(s: SnapType) -> Option<i32> {
         SnapType::Midpoint => 2,
         SnapType::Center => 4,
         SnapType::Node => 8,
+        SnapType::GeometricCenter => 1024,
         SnapType::Quadrant => 16,
         SnapType::Intersection => 32,
         SnapType::Insertion => 64,
@@ -430,6 +432,8 @@ pub struct UserSettings {
     pub cursor_type: CursorType,
     /// Explicit crosshair RGB. `None` keeps automatic background contrast.
     pub crosshair_color: Option<[u8; 3]>,
+    /// Explicit object-snap marker RGB. `None` keeps the automatic colour.
+    pub snap_marker_color: Option<[u8; 3]>,
     /// Model-space lineweight preview scale as a percentage.
     pub lineweight_display_scale: i32,
     /// Isometric drafting changes the grid and crosshair to the active axis
@@ -459,6 +463,9 @@ pub struct UserSettings {
     /// so an intranet folder or a private GitHub raw folder both work.
     #[serde(default)]
     pub font_source_url: String,
+    /// Drawing new tabs start from (QNEW template); empty = a blank drawing.
+    #[serde(default)]
+    pub qnew_template: String,
     /// App version whose donation prompt has been displayed.
     pub donation_prompt_version: String,
     /// The graphics verdict (`GpuStatus::identity()`) whose warning popup the
@@ -819,6 +826,7 @@ impl Default for UserSettings {
             ncopy_bind: false,
             cursor_type: CursorType::Crosshair,
             crosshair_color: None,
+            snap_marker_color: None,
             lineweight_display_scale: 100,
             isometric_drafting: false,
             iso_plane: IsoPlane::Left,
@@ -827,6 +835,7 @@ impl Default for UserSettings {
             default_assoc_prompted: false,
             check_missing_fonts: true,
             font_source_url: String::new(),
+            qnew_template: String::new(),
             donation_prompt_version: String::new(),
             gpu_warning_silenced: String::new(),
             disabled_plugins: Vec::new(),