M8.16: Envelopes bend images, symbols, gradients, patterns and appearance; warps keep their frame

- Images distort as a raster mesh warp: cut by Fidelity into triangles,
  each a clipped image under the affine map of its corners (pieces overlap
  slightly, no seams; the renderer paints them without clip layers; SVG
  writes the pixels once and <use>s them).
- Symbol instances distort as their symbol's art (the renderer's cache
  follows edits to the symbol).
- Distort Appearance bakes strokes (filled outlines) and geometry effects
  before bending; Distort Linear Gradients bends linear gradients; Distort
  Pattern Fills bends the tiles. Opacity masks of the content bend too.
- Bug fix: a rotated, sheared or reflected warp envelope re-warped along
  the page axes. Envelopes now keep their own frame (append-only model
  field), so the warp turns with the art; move and scale keep it square.
- Live evaluation shares one set of hooks (vectorcraft_doc::live::Hooks,
  vectorcraft_effects::{expand_live, expanded_live_group,
  expand_live_deep}) between the canvas, Expand and every exporter.

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

crates/doc/src/node.rs

@@ -275,6 +275,11 @@ pub enum NodeKind {
         /// Envelope Options besides Fidelity.
         #[serde(default, skip_serializing_if = "crate::skip::is_default")]
         options: crate::live::EnvelopeOptions,
+        /// The envelope's own axes (→ the document): the transforms it took since it was made that
+        /// the page axes can't stand for (rotation, shear, reflection). The content maps from its
+        /// bounds in this frame, and a warp bends along it.
+        #[serde(default, skip_serializing_if = "crate::skip::is_default")]
+        frame: Affine,
     },
     /// Gradient mesh.
     Mesh(GradientMesh),
@@ -536,7 +541,7 @@ impl Node {
                 let b = crate::live::nodes_bounds(children);
                 vectorcraft_geom::union_opt(b, spec.spine.as_ref().and_then(|s| s.bounds()))
             }
-            NodeKind::Envelope { content, kind, .. } => crate::live::envelope_bounds(content, kind),
+            NodeKind::Envelope { content, kind, frame, .. } => crate::live::envelope_bounds(content, kind, *frame),
             NodeKind::Mesh(m) => m.bounds(),
             NodeKind::Repeat(r) => r.bounds(),
         }
@@ -639,10 +644,11 @@ impl Node {
                     s.transform(a);
                 }
             }
-            NodeKind::Envelope { content, kind, .. } => {
+            NodeKind::Envelope { content, kind, frame, .. } => {
                 for c in content.iter_mut() {
                     Arc::make_mut(c).transform_scaled(a, sc);
                 }
+                *frame = crate::live::envelope_frame(a * *frame);
                 match kind {
                     EnvelopeKind::Mesh { points, .. } => {
                         for p in points.iter_mut() {