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/io/mod.rs

@@ -170,9 +170,10 @@ impl From<&str> for OpenLoadError {
 pub async fn pick_open_path() -> Option<(PathBuf, u64)> {
     let handle = crate::sys::file_dialog()
         .set_title(crate::t!("Open CAD file").as_ref())
-        .add_filter(crate::t!("CAD Files").as_ref(), &["dwg", "dxf", "bak", "sv$", "DWG", "DXF", "BAK"])
+        .add_filter(crate::t!("CAD Files").as_ref(), &["dwg", "dxf", "dwt", "bak", "sv$", "DWG", "DXF", "DWT", "BAK"])
         .add_filter(crate::t!("DWG Files").as_ref(), &["dwg", "DWG"])
         .add_filter(crate::t!("DXF Files").as_ref(), &["dxf", "DXF"])
+        .add_filter(crate::t!("Drawing Template (*.dwt)").as_ref(), &["dwt", "DWT"])
         .add_filter(crate::t!("Backup / Autosave").as_ref(), &["bak", "sv$", "BAK"])
         .add_filter(crate::t!("All Files").as_ref(), &["*"])
         .pick_file()
@@ -1761,6 +1762,16 @@ mod save_failure_tests {
 /// picked from outside the plot styles folder is copied into it (unless a
 /// file of that name is already there), so the dialog lists it from now on
 /// and page setups naming it resolve after a restart.
+/// Pick a `.lin` linetype definition file and return its text (#1588).
+pub async fn pick_linetype_file() -> Option<String> {
+    let handle = crate::sys::file_dialog()
+        .set_title(crate::t!("Load Linetypes").as_ref())
+        .add_filter(crate::t!("Linetype Files").as_ref(), &["lin", "LIN"])
+        .pick_file()
+        .await?;
+    Some(String::from_utf8_lossy(&handle.read().await).into_owned())
+}
+
 pub async fn pick_plot_style() -> Result<Option<plot_style::PlotStyleTable>, String> {
     let dialog = crate::sys::file_dialog()
         .set_title(crate::t!("Load Plot Style Table").as_ref())