M9: add multiple colored lights to 3D effects

Add opaque RGB light color and up to ten independently adjustable lights to
Revolve, Extrude & Bevel, Inflate and Rotate. Keep light selection, Add/Delete,
selected-light gizmos and preview transactions on the existing command path.

Preserve legacy white-light Inflate polygons, paint composition and seam joins,
including the 0.05 seam minimum. Use shared smooth normals for colored Inflate,
and batch solid-fill RGB channel paths behind one surface clip. Keep source
paths editable and SVG/PDF output vector artwork.

Rebase onto main f7de3d6a, retaining both sides of progress docs and all 22
catalogs. Shade freeform points once through the shared paint mapper. Document
release measurements and a reproducible CLI fixture, including the remaining
source-gradient cost and the one-light timing tradeoff.

Validation: full cargo xtask ci passed all 10 steps; 7,978 tests passed, zero
failed and 11 ignored. Four legacy white-light PNGs match unchanged main byte
for byte. Three paired release bench/perf repetitions completed without busy
warnings; all six standard perf runs passed every budget. Two-light solid
Inflate improved from 136.2 to 96.8 ms/frame at 1200x1200, default eight threads.

docs/revolve.md

@@ -10,8 +10,9 @@ line, give it a nonzero offset. A vertical line at zero offset lies on the axis
 **Revolve angle** sweeps 0 to 360 degrees. **Rotation X/Y/Z** rotates the viewing direction, with all three axes defaulting to 0 degrees. **Perspective**
 runs 0° to 160°, as documented: 0° is an orthographic view, and wider angles bring the eye nearer (see
 [three-d.md](three-d.md#perspective)). **Segments** controls radial resolution (8 to 128 for a full turn).
-Lighting is one directional light with the documented Light Settings (see [three-d.md](three-d.md#lighting)):
-**Intensity**, **Rotation**, **Height**, **Softness** and **Ambient Light**, and **Light behind the object**.
+Lighting supports one to ten directional lights with the documented Light Settings (see [three-d.md](three-d.md#lighting)):
+**Color**, **Intensity**, **Rotation**, **Height**, **Softness** and **Ambient Light**, and **Light behind the object**.
+Color is white by default, with a picker and a reset dot. Colored light preserves neutral ambient illumination.
 Turn **Shading** off to keep the source paint without lighting.
 
 Shaded Revolve surfaces automatically use smooth lighting from the profile's tangents,
@@ -44,7 +45,7 @@ horizontally to turn the light round the object; drag the **Height** line or its
 raise or lower it. The labels remain usable when the ring shrinks to a point (Height 90°).
 Hold Shift to snap to 15-degree increments. Light gestures update their matching fields without
 rotating the object, and keep the same temporary preview, Escape, Cancel and undo behaviour.
-Intensity, Softness and Ambient Light are draggable fields and sliders.
+Intensity, Softness and Ambient Light are draggable fields and sliders. The Lights list selects which light the gizmo and settings edit; Add Light and Delete Light manage up to ten lights, keeping at least one. Ambient is shared and applied once. Preview, Cancel, Reset all and undo include the whole list.
 
 **Shading** off hides the light gizmo and disables lighting controls. Switch to **Rotation** to return
 to the object rings. **Show axis** in **Advanced** displays the source's vertical axis on the object.
@@ -89,7 +90,7 @@ with the standard command.
 - Open profiles have circular end caps by default; turning Cap off keeps them open. Partial-sweep angular cut sides remain open. Closed profile boundaries are swept as provided.
 - One Revolve per source object. Edit its options rather than applying another.
 - Object-level Revolve uses the top visible fill, falling back to a stroke. Per-item Revolve uses that item's paint.
-- Smooth diffuse shading, one directional light, no textures, cast shadows or physical materials. Smooth shading interpolates lighting in projected triangles; it does not smooth the silhouette or add specular highlights.
+- Smooth diffuse shading, one to ten directional lights, no textures, cast shadows or physical materials. Smooth shading interpolates lighting in projected triangles; it does not smooth the silhouette or add specular highlights.
 - Faces use back-to-front depth sorting. Caps facing the camera cover their rim seams; caps facing away sit behind the body. Intersecting profiles can have incorrect visibility.
 - Curves use sixteen samples per segment; profiles are limited to 1,024 samples and surfaces to 32,768 faces. Smooth shaded side quads become two triangles and share that same limit. A continuous cap retains its original radial mesh cost within this limit. Projected ring curves have a 0.001-point fitting tolerance and a shared 32,768-curve limit.
 - Axis, bounds and ordinary selection handles continue to refer to the editable 2D source profile.