.ai import: outlines from the editing data keep their look and threads; mesh corners with non-numbers are unread

Follow-ups to the review of #4697 and #4698:

- With textAs: outlines, a .ai saved without PDF compatibility, read
  from its editing data alone, has its type outlined too, as an empty
  page or a text-only placeholder already did.
- Threaded type read from the editing data holds its story in its first
  frame: it now flows through its frames before it is outlined, so each
  frame's outlines show the text it holds, and the outlined frames
  leave their threads.
- Each outline group keeps its type's opacity, blend mode, isolation,
  opacity mask and effects (the same carry-over the flattener uses).
- A gradient-mesh corner (/N) holding anything but numbers is unread,
  instead of being read with the numbers after it shifted into its
  colour and opacity.

docs/file-format-parity.md

@@ -141,6 +141,7 @@ the app's own editing copy of a file (an EPS after its `%%EOF`, a `.ai`'s `AIPri
 | 2026-10-30 | minor | SVG export: axis-aligned rectangles are written as `<rect>`, circles and ellipses drawn with four standard arcs as `<circle>`/`<ellipse>`, straight lines as `<line>` and other straight-segment paths as `<polygon>`/`<polyline>`, at the written precision; a rectangle or ellipse with a dashed stroke, turned ellipses, curves and compound paths stay `<path>` (#4652); scores unchanged |
 | 2026-10-30 | minor | `.ai` import: a placed (linked) file written as an object's copy on `%_` lines is read: its `%AI5_BeginPlace` and `%AI5_EndPlace` markers there were dropped, so the `~` that ends it was an unknown operator and the whole file came in as its PDF part; its preview's header, on a `%_` line too, is read. Own-fixture test in `import::ai::tests`; scores unchanged |
 | 2026-10-30 | minor | PDF export: an opaque gradient mesh is written as one PDF Type 6 (Coons patch) shading (ISO 32000-1, 8.7.4.5.7) filling its outline, so viewers blend its colours smoothly instead of showing the bands and seams of the 8 × 8 flat quads a patch it was cut into; a file of 65,558 small meshes exports in 14 s instead of 56 s, at half the size. A mesh with see-through points is still written as quads. Own-fixture tests in `tests::mesh_export`; scores unchanged |
+| 2026-10-30 | minor | `.ai` import with `textAs: "outlines"`, read from the editing data alone: a file saved without PDF compatibility has its type outlined too; threaded type flows through its frames before it is outlined, so each frame's outlines show the text it holds; and each outline group keeps its type's opacity, blending, opacity mask and effects. `.ai`/EPS import: a gradient-mesh corner holding anything but numbers is unread instead of read with the numbers after it shifted into its colour and opacity. Tests in `tests_aiimport.rs` and `import::ai::mesh::tests`; scores and hours unchanged |
 | 2026-10-30 | minor | `.ai` import: a PDF part counts as an empty page only when nothing on it was skipped (an image that can't be decoded draws nothing too), so such a page keeps its notes and is checked against the editing data as before; with `textAs: "outlines"`, a file read from its editing data alone (an empty page, or the text-only placeholder of #1387) has its type outlined. Tests in `tests_aiimport.rs`; scores and hours unchanged |
 | 2026-10-30 | minor | `.ai` import: a file whose PDF part is an empty page opens from its editing data where that reads, instead of opening blank; scores unchanged |
 | 2026-10-30 | minor | `.ai` import: a file whose PDF part's pages are cropped to its art rather than its artboards no longer comes in as that PDF part (each page a copy of all the art) but from its layers, with its artboards, where they draw as the page does; own-fixture test in `tests_aiimport`; scores unchanged |