refactor(wire): add WireModel.points_low parallel buffer (empty default)

Foundation for double-single positions: WireModel now carries an
index-paired f32 residual buffer (`points_low`) next to the existing
`points` high half. Empty means "all-zero residual", so every existing
constructor (interactive draw, previews) is unchanged in behaviour;
tessellation from CAD f64 will fill it in the next steps so vertex
precision survives at UTM-scale coordinates.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/modules/annotate/aligned_dim.rs

@@ -94,6 +94,7 @@ impl CadCommand for AlignedDimensionCommand {
         Some(WireModel {
             name: "dimaligned_preview".into(),
             points: vec![[p1.x, p1.y, p1.z], [p2.x, p2.y, p2.z]],
+            points_low: Vec::new(),
             color: WireModel::CYAN,
             selected: false,
             pattern_length: 0.0,
@@ -134,6 +135,7 @@ fn preview_aligned(p1: Vec3, p2: Vec3, dim_pt: Vec3) -> WireModel {
             [d1.x, d1.y, d1.z],
             [d2.x, d2.y, d2.z],
         ],
+        points_low: Vec::new(),
         color: WireModel::CYAN,
         selected: false,
         pattern_length: 0.0,

src/modules/annotate/angular_dim.rs

@@ -126,6 +126,7 @@ fn preview_wire(points: Vec<Vec3>) -> WireModel {
     WireModel {
         name: "dimangular_preview".to_string(),
         points: points.into_iter().map(|p| [p.x, p.y, p.z]).collect(),
+        points_low: Vec::new(),
         color: WireModel::CYAN,
         selected: false,
         pattern_length: 0.0,

src/modules/annotate/diameter_dim.rs

@@ -97,6 +97,7 @@ fn preview_line(a: Vec3, b: Vec3) -> WireModel {
     WireModel {
         name: "dimdia_preview".into(),
         points: vec![[a.x, a.y, a.z], [b.x, b.y, b.z]],
+        points_low: Vec::new(),
         color: WireModel::CYAN,
         selected: false,
         pattern_length: 0.0,

src/modules/annotate/dim_baseline.rs

@@ -155,6 +155,7 @@ impl CadCommand for DimBaselineCommand {
                 [dim_line_pt.x, dim_line_pt.y, dim_line_pt.z],
                 [dim_line_pt2.x, dim_line_pt2.y, dim_line_pt2.z],
             ],
+            points_low: Vec::new(),
             color: WireModel::CYAN,
             selected: false,
             pattern_length: 0.0,

src/modules/annotate/dim_continue.rs

@@ -135,6 +135,7 @@ impl CadCommand for DimContinueCommand {
                 [dim_line_pt.x, dim_line_pt.y, dim_line_pt.z],
                 [dim_line_pt2.x, dim_line_pt2.y, dim_line_pt2.z],
             ],
+            points_low: Vec::new(),
             color: WireModel::CYAN,
             selected: false,
             pattern_length: 0.0,

src/modules/annotate/dimjogline.rs

@@ -92,6 +92,7 @@ impl CadCommand for DimJogLineCommand {
                 [pt.x + d * 0.3, pt.y, pt.z - d],
                 [pt.x + d, pt.y, pt.z],
             ],
+            points_low: Vec::new(),
             color: WireModel::CYAN,
             selected: false,
             pattern_length: 0.0,

src/modules/annotate/dimtedit.rs

@@ -106,6 +106,7 @@ impl CadCommand for DimTeditCommand {
                 [pt.x - d, pt.y, pt.z + d],
                 [pt.x - d, pt.y, pt.z - d],
             ],
+            points_low: Vec::new(),
             color: WireModel::CYAN,
             selected: false,
             pattern_length: 0.0,

src/modules/annotate/leader_cmd.rs

@@ -165,6 +165,7 @@ fn preview_wire(pts: &[Vec3]) -> WireModel {
     WireModel {
         name: "leader_preview".into(),
         points,
+        points_low: Vec::new(),
         color: WireModel::CYAN,
         selected: false,
         pattern_length: 0.0,

src/modules/annotate/linear_dim.rs

@@ -133,6 +133,7 @@ fn preview_wire(points: Vec<Vec3>) -> WireModel {
     WireModel {
         name: "dimlinear_preview".to_string(),
         points: points.into_iter().map(|p| [p.x, p.y, p.z]).collect(),
+        points_low: Vec::new(),
         color: WireModel::CYAN,
         selected: false,
         pattern_length: 0.0,

src/modules/annotate/mleader_cmd.rs

@@ -151,6 +151,7 @@ fn preview_wire(pts: &[Vec3]) -> WireModel {
     WireModel {
         name: "mleader_preview".into(),
         points,
+        points_low: Vec::new(),
         color: WireModel::CYAN,
         selected: false,
         pattern_length: 0.0,

src/modules/annotate/mleader_edit.rs

@@ -458,6 +458,7 @@ fn preview_wire(pts: &[Vec3]) -> WireModel {
     WireModel {
         name: "mleader_edit_preview".into(),
         points: pts.iter().map(|p| [p.x, p.y, p.z]).collect(),
+        points_low: Vec::new(),
         color: WireModel::CYAN,
         selected: false,
         pattern_length: 0.0,

src/modules/annotate/qdim.rs

@@ -90,6 +90,7 @@ impl CadCommand for QdimCommand {
         Some(WireModel {
             name: "qdim_preview".into(),
             points: vec![[pt.x - d * 3.0, pt.y, pt.z], [pt.x + d * 3.0, pt.y, pt.z]],
+            points_low: Vec::new(),
             color: WireModel::CYAN,
             selected: false,
             pattern_length: 0.0,

src/modules/annotate/radius_dim.rs

@@ -102,6 +102,7 @@ fn preview_wire(points: Vec<Vec3>) -> WireModel {
     WireModel {
         name: "dimradius_preview".to_string(),
         points: points.into_iter().map(|p| [p.x, p.y, p.z]).collect(),
+        points_low: Vec::new(),
         color: WireModel::CYAN,
         selected: false,
         pattern_length: 0.0,

src/modules/annotate/table_cmd.rs

@@ -150,6 +150,7 @@ impl CadCommand for TableCommand {
                     [x, y, z - h],
                     [x, y, z],
                 ],
+                points_low: Vec::new(),
                 color: WireModel::CYAN,
                 selected: false,
                 pattern_length: 0.0,

src/modules/annotate/tolerance_cmd.rs

@@ -92,6 +92,7 @@ impl CadCommand for ToleranceCommand {
                 [pt.x, pt.y, pt.z - d],
                 [pt.x, pt.y, pt.z + d],
             ],
+            points_low: Vec::new(),
             color: WireModel::CYAN,
             selected: false,
             pattern_length: 0.0,