feat(dgn-ls): dash walls from start + fix wall connector and cap identity

DET pipe walls now carry the stroke pattern (dash_from_start), which
tiles from each wall's own start vertex and skips the A-type end
alignment that was force-lighting a solid dash under the end symbol.

Two rendering fixes on top:
- Dedup the host polyline's vertices before offsetting the walls. Some
  DGN pipe polylines carry trailing duplicate end vertices; a zero-length
  segment gave offset_xy a degenerate normal, leaving that vertex
  un-offset and folding the wall down to the centre line. The two walls'
  fold segments met at the centre and drew a spurious line linking them.
- Re-key the symbol (end circle / half-ellipse) wires to the host handle
  so the whole pipe picks and selects as one entity instead of the
  symbols acting as separate phantom entities.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/modules/annotate/aligned_dim.rs

@@ -186,6 +186,7 @@ impl CadCommand for AlignedDimensionCommand {
         let p1 = p1.as_vec3();
         let p2 = p2.as_vec3();
         Some(WireModel {
+            dash_from_start: false,
             text_verts: Vec::new(),
             name: "dimaligned_preview".into(),
             points: vec![[p1.x, p1.y, p1.z], [p2.x, p2.y, p2.z]],
@@ -233,6 +234,7 @@ fn preview_aligned(p1: DVec3, p2: DVec3, dim_pt: DVec3) -> WireModel {
     let d1 = d1.as_vec3();
     let d2 = d2.as_vec3();
     WireModel {
+            dash_from_start: false,
             text_verts: Vec::new(),
         name: "dimaligned_preview".into(),
         points: vec![

src/modules/annotate/angular_dim.rs

@@ -130,6 +130,7 @@ fn v3(pt: DVec3) -> Vector3 {
 
 fn preview_wire(points: Vec<Vec3>) -> WireModel {
     WireModel {
+            dash_from_start: false,
             text_verts: Vec::new(),
         name: "dimangular_preview".to_string(),
         points: points.into_iter().map(|p| [p.x, p.y, p.z]).collect(),

src/modules/annotate/diameter_dim.rs

@@ -180,6 +180,7 @@ fn v3(p: DVec3) -> Vector3 {
 
 fn preview_line(a: Vec3, b: Vec3) -> WireModel {
     WireModel {
+            dash_from_start: false,
             text_verts: Vec::new(),
         name: "dimdia_preview".into(),
         points: vec![[a.x, a.y, a.z], [b.x, b.y, b.z]],

src/modules/annotate/dim_baseline.rs

@@ -179,6 +179,7 @@ impl CadCommand for DimBaselineCommand {
         let dim_line_pt2 = dim_line_pt2.as_vec3();
         let pt = pt.as_vec3();
         Some(WireModel {
+            dash_from_start: false,
             text_verts: Vec::new(),
             name: "dimbase_preview".into(),
             points: vec![

src/modules/annotate/dim_continue.rs

@@ -159,6 +159,7 @@ impl CadCommand for DimContinueCommand {
         let dim_line_pt = p1 + perp * (dim_line_perp - p1.dot(perp));
         let dim_line_pt2 = pt + perp * (dim_line_perp - pt.dot(perp));
         Some(WireModel {
+            dash_from_start: false,
             text_verts: Vec::new(),
             name: "dimcont_preview".into(),
             points: vec![

src/modules/annotate/dimjogline.rs

@@ -85,6 +85,7 @@ impl CadCommand for DimJogLineCommand {
         }
         let d = 0.3_f32;
         Some(WireModel {
+            dash_from_start: false,
             text_verts: Vec::new(),
             name: "dimjog_preview".into(),
             // Jog zigzag in the XY drawing plane (Z is elevation, ~0). The old

src/modules/annotate/dimtedit.rs

@@ -100,6 +100,7 @@ impl CadCommand for DimTeditCommand {
         }
         let d = 0.2_f32;
         Some(WireModel {
+            dash_from_start: false,
             text_verts: Vec::new(),
             name: "dimtedit_preview".into(),
             // Marker box in the XY drawing plane (Z is elevation, ~0). The old

src/modules/annotate/leader_cmd.rs

@@ -163,6 +163,7 @@ fn preview_wire(pts: &[Vec3]) -> WireModel {
         points.push([w2.x, w2.y, w2.z]);
     }
     WireModel {
+            dash_from_start: false,
             text_verts: Vec::new(),
         name: "leader_preview".into(),
         points,

src/modules/annotate/linear_dim.rs

@@ -218,6 +218,7 @@ fn v3(pt: DVec3) -> Vector3 {
 
 fn preview_wire(points: Vec<DVec3>) -> WireModel {
     WireModel {
+            dash_from_start: false,
             text_verts: Vec::new(),
         name: "dimlinear_preview".to_string(),
         points: points

src/modules/annotate/mleader_cmd.rs

@@ -150,6 +150,7 @@ fn preview_wire(pts: &[Vec3]) -> WireModel {
         points.push([w2.x, w2.y, w2.z]);
     }
     WireModel {
+            dash_from_start: false,
             text_verts: Vec::new(),
         name: "mleader_preview".into(),
         points,

src/modules/annotate/mleader_edit.rs

@@ -458,6 +458,7 @@ impl CadCommand for MLeaderCollectCommand {
 
 fn preview_wire(pts: &[Vec3]) -> WireModel {
     WireModel {
+            dash_from_start: false,
             text_verts: Vec::new(),
         name: "mleader_edit_preview".into(),
         points: pts.iter().map(|p| [p.x, p.y, p.z]).collect(),

src/modules/annotate/ordinate_dim.rs

@@ -121,6 +121,7 @@ fn ordinate_elbow(feature: DVec3, leader: DVec3, is_x: bool) -> DVec3 {
 
 fn preview_wire(points: Vec<Vec3>) -> WireModel {
     WireModel {
+            dash_from_start: false,
             text_verts: Vec::new(),
         name: "dimordinate_preview".into(),
         points: points.into_iter().map(|p| [p.x, p.y, p.z]).collect(),

src/modules/annotate/qdim.rs

@@ -90,6 +90,7 @@ impl CadCommand for QdimCommand {
         }
         let d = 0.5_f32;
         Some(WireModel {
+            dash_from_start: false,
             text_verts: Vec::new(),
             name: "qdim_preview".into(),
             points: vec![[pt.x - d * 3.0, pt.y, pt.z], [pt.x + d * 3.0, pt.y, pt.z]],

src/modules/annotate/radius_dim.rs

@@ -185,6 +185,7 @@ fn v3(pt: DVec3) -> Vector3 {
 
 fn preview_wire(points: Vec<Vec3>) -> WireModel {
     WireModel {
+            dash_from_start: false,
             text_verts: Vec::new(),
         name: "dimradius_preview".to_string(),
         points: points.into_iter().map(|p| [p.x, p.y, p.z]).collect(),

src/modules/annotate/table_cmd.rs

@@ -139,6 +139,7 @@ impl CadCommand for TableCommand {
             let y = pt.y;
             let z = pt.z;
             Some(WireModel {
+            dash_from_start: false,
             text_verts: Vec::new(),
                 name: "table_preview".into(),
                 points: vec![

src/modules/annotate/tolerance_cmd.rs

@@ -84,6 +84,7 @@ impl CadCommand for ToleranceCommand {
         }
         let d = 0.15_f32;
         Some(WireModel {
+            dash_from_start: false,
             text_verts: Vec::new(),
             name: "tolerance_preview".into(),
             points: vec![