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/home/modify/break_cmd.rs

@@ -7,8 +7,6 @@
 //
 //   BREAK @ (at-sign as second point) → Break at a single point (splits without gap).
 
-use std::f64::consts::TAU;
-
 use acadrust::entities::{Arc as ArcEnt, Line as LineEnt, LwPolyline};
 use acadrust::types::Vector3;
 use acadrust::{EntityType, Handle};
@@ -20,6 +18,7 @@ use crate::scene::wire_model::WireModel;
 
 // ── Ribbon definition ──────────────────────────────────────────────────────
 
+#[allow(dead_code)]
 pub fn tool() -> ToolDef {
     ToolDef {
         id: "BREAK",
@@ -285,3 +284,50 @@ impl CadCommand for BreakInteractiveCommand {
         None
     }
 }
+
+// ── BREAKATPOINT (BAP) — split at a single point, no gap ──────────────────
+
+pub struct BreakAtPointCommand {
+    target: Option<Handle>,
+}
+
+impl BreakAtPointCommand {
+    pub fn new() -> Self {
+        Self { target: None }
+    }
+}
+
+impl CadCommand for BreakAtPointCommand {
+    fn name(&self) -> &'static str { "BREAKATPOINT" }
+
+    fn prompt(&self) -> String {
+        if self.target.is_none() {
+            "BREAKATPOINT  Select object:".into()
+        } else {
+            "BREAKATPOINT  Specify break point:".into()
+        }
+    }
+
+    fn needs_entity_pick(&self) -> bool {
+        self.target.is_none()
+    }
+
+    fn on_entity_pick(&mut self, handle: Handle, _pt: Vec3) -> CmdResult {
+        if handle.is_null() {
+            return CmdResult::NeedPoint;
+        }
+        self.target = Some(handle);
+        CmdResult::NeedPoint
+    }
+
+    fn on_point(&mut self, pt: Vec3) -> CmdResult {
+        match self.target {
+            Some(handle) => CmdResult::BreakEntity { handle, p1: pt, p2: pt },
+            None => CmdResult::Cancel,
+        }
+    }
+
+    fn on_enter(&mut self) -> CmdResult {
+        CmdResult::Cancel
+    }
+}