Effects: a painted clipping path's fill and stroke effects apply before a group's

A clipping path that paints a fill or stroke kept the geometry effects of
those fills and strokes live, so a geometry effect on the clip group or on
a group around it reshaped the path first and the fill's or stroke's
effect applied after it, on the canvas and in export alike. Unpainted
clipping paths already applied them first.

The clipping path now becomes one path per fill and stroke with those
effects applied, as an unpainted one does, in a group marked as such
pieces (`NodeExtras::clip_pieces`, saved with the document). `clip_paint`
paints that group's fill pieces behind the clipped art and its stroke
pieces over it, as the path paints its fills and strokes, also after an
effect around it turns a piece into a compound path or puts it in a group.
The clip group's visual bounds take in the stroke pieces' width, and HP-GL
export draws the clipping path once, in its stroke pieces.

An export of a painted clipping path with such effects in a clip group
without effects of its own also keeps its fill and stroke now, where the
baked pieces painted nothing.

docs/target-app-parity.md

@@ -1658,7 +1658,7 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
     Object › Expand Appearance keeps each stroke of a path a stroke (weight, caps, joins, dashes, arrowheads, alignment and width profile) on a copy of the path with the geometry effects baked in, and Object › Expand… is dimmed, with a tooltip, while the selection has appearance attributes, so a stroked line with Zig Zag becomes a stroked zig-zag line and only Expand then outlines it, the two steps the [Expand objects](https://helpx.adobe.com/illustrator/desktop/manage-objects/arrange-objects/expand-objects.html) help page describes (#3089). Brushed strokes still become their brush art; `object.expand` still bakes and outlines in one step for agents.
   - **Masks and clipping:** opacity-mask controls work while the mask is being edited; transparency commands take ids and work without a selection; clipping sets clip by compound paths, even-odd paths, text and groups on screen and in raster export, matching SVG/PDF. Alt-click shows only the mask; SVG masks keep Clip and Invert; the transparency grid is per-document state; a clipping path's own fill and stroke paint behind and over the clipped art; layers can be clipping masks.
   - **Masks and clipping:** opacity-mask controls work while the mask is being edited; transparency commands take ids and work without a selection; clipping sets clip by compound paths, even-odd paths, text and groups on screen and in raster export, matching SVG/PDF. Alt-click shows only the mask; SVG masks keep Clip and Invert; the transparency grid is per-document view state saved in native files (#1968); a clipping path's own fill and stroke paint behind and over the clipped art; layers can be clipping masks.
-    The geometry effects of a clipping path (Roughen, Transform and the other effects that reshape a path), of its fills and strokes, and of the members of a group used as one, shape the area it clips to on the canvas and in raster export, as in SVG and PDF export: a roughened clipping path clips by its roughened outline. They apply before the geometry effects of the clip group or of a group around it, on the canvas and in every export. When the clipping path has a fill or stroke of its own, the geometry effects of those fills and strokes apply after the group's geometry effects instead. Type used as a clipping path keeps its geometry effects when a group's effect outlines it. Raster effects such as Gaussian Blur leave that area as it is. `effects::tests::clipfx` and the renderer's `tests::clip` cover it.
+    The geometry effects of a clipping path (Roughen, Transform and the other effects that reshape a path), of its fills and strokes, and of the members of a group used as one, shape the area it clips to on the canvas and in raster export, as in SVG and PDF export: a roughened clipping path clips by its roughened outline. They apply before the geometry effects of the clip group or of a group around it, on the canvas and in every export, also when the clipping path paints a fill or stroke of its own: that fill and stroke draw the shapes their effects give them. Type used as a clipping path keeps its geometry effects when a group's effect outlines it. Raster effects such as Gaussian Blur leave that area as it is. `effects::tests::clipfx` and the renderer's `tests::clip` cover it.
     Clicks, Select Behind, the Unlock submenu, marquees and the Enclosing Lasso inside a clip group or a clipping layer follow that area too: the clipped art is found where the effects moved it and not where they took it away. The clipping path itself is still found by its own outline and anchors. A hidden member of a group used as a clipping path does not clip, and a geometry effect on it does not change where clicks land. Outline view and layers with Preview off draw the plain clipping path, and clicks and marquees there count it. Direct Selection picks and outlines an object of a dynamic symbol's art by the same rules. `doc::hit::tests` and the engine's `tests::clip` cover it.
   - **Transparency:** three-state Knockout Group (on, neutral, off), Opacity & Mask Define Knockout Shape, Page Isolated Blending and Page Knockout Group, on screen and in SVG/PDF. SVG export writes a knockout group of opaque art plainly, without masks, so shapes meeting edge to edge leave no seam; translucent, blended, masked or brushed art knocks out through masks. Blend modes match the standard formulas on screen, in SVG and in PDF, and non-isolated groups blend with the art below. Flatten Transparency with presets, a dialog and a Flattener Preview panel. Flattening for files without transparency (PDF/X-1a, PDF/X-3) in a CMYK document keeps the inks where it rasterizes, as under an image with see-through pixels: the images it makes hold ink amounts, not screen colours the file would separate again, so a C100 M6 Y41 K3 panel stays C100 M6 Y41 K3 there (#2160, `engine/src/cmd/fileio/tests_pdfx.rs`).
     On the canvas, the renderer no longer draws the picture of the art below back as an image each time it copies the backdrop of a non-isolated group that blends: it keeps that picture and draws the art that follows over it. At 2880 × 1800, 50 translucent groups with Multiply members take 65 ms a frame instead of 299 ms on 8 threads (`vectorcraft-cli bench`), and the frames have the same pixels.