M3.8: split the paint/panel command modules and the dialogs into per-area files

No behaviour change: every command keeps its id, label, menu, shortcut and
params doc.

- Engine: swatch.* -> cmd/swatch.rs, graphicStyle.* -> cmd/style.rs,
  appearance.* (incl. copyFrom) -> cmd/appearance.rs, stroke.set/setAdvanced
  -> cmd/stroke.rs, paint.editGradient/setGradientGeom -> cmd/gradient.rs.
  Shared helpers in cmd/mod.rs: leaf_targets/paint_targets (replacing three
  copies) and unique_name (swatch and graphic style naming).
- UI: dialogs.rs -> dialogs/ with one file per dialog and a DialogSpec
  registry (one DialogKind row per dialog); shared field widgets in
  dialogs/form.rs. Headless frame tests draw and confirm every dialog.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/engine/src/cmd/xform.rs

@@ -1,9 +1,9 @@
-//! Commands backing transform/utility tools: free distort, eyedropper, gradient vector, artboard move.
+//! Commands backing transform/utility tools: free distort, eyedropper colour sampling, artboard move.
 
 use std::sync::Arc;
 
 use serde_json::{Value, json};
-use vectorcraft_color::{Gradient, GradientGeom, GradientPaint, Paint};
+use vectorcraft_color::Paint;
 use vectorcraft_doc::{Appearance, Node, NodeId, NodeKind};
 use vectorcraft_geom::{Affine, Point, Rect, Vec2};
 
@@ -22,15 +22,6 @@ pub fn specs() -> Vec<CommandSpec> {
             has_doc,
             distort
         ),
-        cmd!(
-            "appearance.copyFrom",
-            "Eyedropper",
-            [],
-            None,
-            "{source: id, ids?} copy fill, stroke, weight, opacity and blend from `source` to ids (default: selection) and to the paint defaults",
-            has_doc,
-            copy_from
-        ),
         cmd!(
             "paint.sampleColor",
             "Sample Color",
@@ -40,15 +31,6 @@ pub fn specs() -> Vec<CommandSpec> {
             has_doc,
             sample_color
         ),
-        cmd!(
-            "paint.setGradientGeom",
-            "Gradient Vector",
-            [],
-            None,
-            "{start: [x,y], end: [x,y], ids?, stroke?: bool} set the gradient vector (solid paints become the default gradient)",
-            has_doc,
-            set_gradient_geom
-        ),
         cmd!(
             "artboard.move",
             "Move Artboard",
@@ -190,72 +172,6 @@ fn distort(s: &mut Session, p: &Value) -> Result<Value> {
 
 // ---------- eyedropper ----------
 
-/// Leaves whose appearance a paint command changes (groups expand to their contents; compound
-/// paths own their children's appearance).
-fn leaf_targets(s: &Session, ids: &[NodeId]) -> Result<Vec<NodeId>> {
-    let d = &s.doc()?.doc;
-    let mut out = vec![];
-    for id in ids {
-        let Some(n) = d.node(*id) else { continue };
-        match &n.kind {
-            NodeKind::Group { .. } | NodeKind::Layer { .. } => n.walk(&mut |c| {
-                if !c.is_container() || matches!(c.kind, NodeKind::Compound { .. }) {
-                    out.push(c.id)
-                }
-            }),
-            _ => out.push(*id),
-        }
-    }
-    let comp: Vec<NodeId> = out.iter().filter(|id| matches!(d.node(**id).map(|n| &n.kind), Some(NodeKind::Compound { .. }))).copied().collect();
-    out.retain(|id| !comp.iter().any(|c| d.parent_of(*id) == Some(*c)));
-    Ok(out)
-}
-
-fn copy_from(s: &mut Session, p: &Value) -> Result<Value> {
-    let src_id = id_param(p, "source").ok_or_else(|| bad("appearance.copyFrom", "missing `source` id"))?;
-    let src = s.doc()?.doc.node(src_id).cloned().ok_or(EngineError::NoNode(src_id))?;
-    let appearance = match &src.kind {
-        NodeKind::Text(t) => match t.runs.first() {
-            Some(r) => Appearance::basic(r.style.fill.clone(), r.style.stroke.clone(), r.style.stroke_width),
-            None => src.appearance.clone(),
-        },
-        _ => src.appearance.clone(),
-    };
-    s.paint.fill = appearance.fill_paint();
-    s.paint.stroke = appearance.stroke_paint();
-    if appearance.stroke().is_some() {
-        s.paint.stroke_width = appearance.stroke_width();
-    }
-    let ids = match ids_param(p, "ids") {
-        Some(v) => v,
-        None => selected_roots(s)?,
-    };
-    let mut targets = leaf_targets(s, &ids)?;
-    targets.retain(|id| *id != src_id);
-    if targets.is_empty() {
-        return Ok(json!({ "ids": [] }));
-    }
-    let (opacity, blend) = (src.opacity, src.blend);
-    s.edit("Eyedropper", |d, _| {
-        for id in &targets {
-            let Some(n) = d.node_mut(*id) else { continue };
-            n.opacity = opacity;
-            n.blend = blend;
-            if let NodeKind::Text(t) = &mut n.kind {
-                for r in &mut t.runs {
-                    r.style.fill = appearance.fill_paint();
-                    r.style.stroke = appearance.stroke_paint();
-                    r.style.stroke_width = appearance.stroke_width();
-                }
-                continue;
-            }
-            n.appearance = appearance.clone();
-        }
-        Ok(())
-    })?;
-    Ok(json!({ "ids": targets.iter().map(|i| i.0).collect::<Vec<_>>() }))
-}
-
 fn sample_color(s: &mut Session, p: &Value) -> Result<Value> {
     let stroke = p.get("stroke").and_then(Value::as_bool).unwrap_or(!s.fill_active);
     let c = p.get("color").ok_or_else(|| bad("paint.sampleColor", "missing color"))?;
@@ -268,46 +184,6 @@ fn sample_color(s: &mut Session, p: &Value) -> Result<Value> {
     (spec.run)(s, &q)
 }
 
-// ---------- gradient tool ----------
-
-fn set_gradient_geom(s: &mut Session, p: &Value) -> Result<Value> {
-    let start = point_param(p, "start").ok_or_else(|| bad("paint.setGradientGeom", "missing start [x,y]"))?;
-    let end = point_param(p, "end").ok_or_else(|| bad("paint.setGradientGeom", "missing end [x,y]"))?;
-    let stroke = bool_or(p, "stroke", false);
-    let ids = match ids_param(p, "ids") {
-        Some(v) => v,
-        None => selected_roots(s)?,
-    };
-    let targets = leaf_targets(s, &ids)?;
-    if targets.is_empty() {
-        return Err(EngineError::Other("nothing selected".into()));
-    }
-    s.edit("Gradient", |d, _| {
-        for id in &targets {
-            let Some(n) = d.node_mut(*id) else { continue };
-            if matches!(n.kind, NodeKind::Text(_)) {
-                continue;
-            }
-            let cur = if stroke { n.appearance.stroke_paint() } else { n.appearance.fill_paint() };
-            let mut gp = match cur {
-                Paint::Gradient(g) => *g,
-                _ => GradientPaint::new(Gradient::default()),
-            };
-            let aspect = gp.geom.map(|g| g.aspect).unwrap_or(1.0);
-            gp.geom = Some(GradientGeom { start, end, aspect });
-            gp.angle = GradientGeom { start, end, aspect }.angle_deg();
-            let paint = Paint::Gradient(Box::new(gp));
-            if stroke {
-                n.appearance.set_stroke(paint);
-            } else {
-                n.appearance.set_fill(paint);
-            }
-        }
-        Ok(())
-    })?;
-    Ok(json!({ "ids": targets.iter().map(|i| i.0).collect::<Vec<_>>() }))
-}
-
 // ---------- artboards ----------
 
 fn artboard_move(s: &mut Session, p: &Value) -> Result<Value> {