Feat: ROADMAP Phase 1-5 batch — trim/extend, plot scale, viewport UX, mline caps, table alignment

- TRIM/EXTEND: Ray and XLine entities supported as cutting boundaries and trim targets;
  trim results in Ray→Line/Ray, XLine→Ray/Ray or Line; hover preview added
- Plot scale override: Fit/1:1/1:2/1:5/1:10/1:20/1:50/1:100/2:1 buttons added to Page Setup
  panel; PageSetupCommit applies scale to PlotSettings
- Viewport UX: locked viewport gets orange border; selected viewport gets white border
- Named view → viewport assignment: Choice dropdown in properties panel copies
  view_target/direction/height to the viewport entity
- MLine caps: perpendicular start/end cap lines added for open (non-closed) MLines
- Wipeout polygon grips: boundary vertices become editable grips when clipping_enabled+Polygonal;
  world→pixel back-projection on drag
- Table cell alignment: CellStyle.alignment (1-9) drives left/center/right + top/middle/bottom
  text positioning; cxf::measure_text() helper added
- New commands/features: DIMCONTINUE (DCO), DIMBASELINE (DBA), TOLERANCE (TOL), TABLE,
  ATTDEF, ATTEDIT, ATTDISP, BREAKATPOINT (BAP), PLOTWINDOW (PW), MLINE (ML);
  DIMSTYLE/DIMCURRENT/CLAYER/LTSCALE/CELTSCALE/SCALETEXT/XDATA/UCSICON/REGEN/DRAWORDER extended
- PLINE arc mode: A/L/CLOSE text input, bulge computation, arc preview
- Warning cleanup: removed unused imports and unreachable patterns

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/modules/view/mod.rs

@@ -15,6 +15,7 @@ mod xray;
 mod zoom_ext;
 mod zoom_in;
 mod zoom_out;
+pub mod plot_window;
 pub mod zoom_window;
 
 use crate::modules::{CadModule, RibbonGroup};

src/modules/view/plot_window.rs

@@ -0,0 +1,66 @@
+// PLOTWINDOW command — pick two corners to define the plot window area.
+//
+// Works only in paper space layouts. After picking P1 and P2, writes the
+// window to the layout's PlotSettings (PlotType::Window).
+
+use crate::command::{CadCommand, CmdResult};
+use crate::scene::wire_model::WireModel;
+use glam::Vec3;
+
+pub struct PlotWindowCommand {
+    p1: Option<Vec3>,
+}
+
+impl PlotWindowCommand {
+    pub fn new() -> Self {
+        Self { p1: None }
+    }
+}
+
+impl CadCommand for PlotWindowCommand {
+    fn name(&self) -> &'static str { "PLOTWINDOW" }
+
+    fn prompt(&self) -> String {
+        if self.p1.is_none() {
+            "PLOTWINDOW  Specify first corner of plot window:".into()
+        } else {
+            "PLOTWINDOW  Specify opposite corner:".into()
+        }
+    }
+
+    fn on_point(&mut self, pt: Vec3) -> CmdResult {
+        match self.p1 {
+            None => {
+                self.p1 = Some(pt);
+                CmdResult::NeedPoint
+            }
+            Some(p1) => CmdResult::SetPlotWindow { p1, p2: pt },
+        }
+    }
+
+    fn on_enter(&mut self) -> CmdResult {
+        CmdResult::Cancel
+    }
+
+    fn on_mouse_move(&mut self, pt: Vec3) -> Option<WireModel> {
+        let p1 = self.p1?;
+        // Draw the selection rectangle.
+        Some(WireModel {
+            name: "plotwindow_preview".into(),
+            points: vec![
+                [p1.x, p1.y, p1.z], [pt.x, p1.y, p1.z],
+                [pt.x, p1.y, p1.z], [pt.x, pt.y, pt.z],
+                [pt.x, pt.y, pt.z], [p1.x, pt.y, pt.z],
+                [p1.x, pt.y, pt.z], [p1.x, p1.y, p1.z],
+            ],
+            color: WireModel::CYAN,
+            selected: false,
+            pattern_length: 0.0,
+            pattern: [0.0; 8],
+            line_weight_px: 1.0,
+            snap_pts: vec![],
+            tangent_geoms: vec![],
+            key_vertices: vec![],
+        })
+    }
+}