.ai import: envelopes open as live envelopes

An envelope in a .ai's editing data opened as its distorted art, with
its mesh and contents dropped. It now opens as a live envelope of its
contents: a warp with its style, bend, distortions and orientation, a
mesh with its points and handles, or a top object with its outline,
with Envelope Options, Fidelity and Edit Contents.

The envelope replaces its drawn art only when VectorCraft draws it like
that art, with a budget so that live envelopes don't make the file open
from its PDF part. When the layers still differ too much from the page,
the drawn art is put back. An envelope that can't be read, or that
draws differently, keeps its drawn art with a note. Envelopes of type
keep their drawn art and hidden type as before.

docs/target-app-parity.md

@@ -1068,6 +1068,7 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
     When the editing data of a `.ai` or EPS is for a page of another size than the file's, the warning that its layers weren't read gives both sizes in points, and the scale of the editing data's page to the file's page (1:10 for a tenth of its size) when their sides are in proportion (#2034; `crates/eps/src/import/tests_native.rs`).
     A `.ai`, or a PDF saved with Illustrator's editing data, whose editing data can't be decompressed opens from its PDF part with a warning that its layers weren't read and why, and an export or Save As to its own path asks first (`acknowledgeLoss`), as for a file whose layers the reader can't read (`crates/eps/src/import/tests_native.rs`, `crates/engine/src/cmd/fileio/tests_aiimport.rs`).
     A `.ai` or EPS opened from its editing data with one object on a shown layer that the reader can't read (an unknown operator inside a group, a pattern fill whose pattern it doesn't have, a symbol instance, a placed file without a usable preview) keeps its layers and groups: in that object's place, its layer gets a group of the page's objects inside the object's box, named after it, with a warning that lists what came in as the page's art and an export or Save As to its own path asking first (`acknowledgeLoss`). The file still opens from its page or PDF part when no box can be found, when live art or another unread object shares the page art inside it, when the object spans two artboards, or when the page art doesn't carry the object's transparency (#4806; `crates/eps/src/import/tests_native.rs`, `crates/engine/src/cmd/fileio/tests_aiimport.rs`).
+    In a `.ai` opened from its editing data, an envelope made with a warp, a mesh or a top object opens as a live envelope of its contents, with its warp style, bend and distortions, its mesh points and handles or its top object's outline, its Envelope Options, its Fidelity and whether its contents are being edited. An envelope that can't be read, or that VectorCraft draws differently from the file's drawn art, keeps that drawn art, with a note. An envelope of type keeps its drawn art, with its type hidden (`crates/eps/src/import/ai/tests.rs`, `crates/eps/src/import/tests_native.rs`).
     PDF export and `.ai` saves write a page with a side longer than 14,400 pt with a `UserUnit` (PDF 1.6), its longer side divided by 14,400 and rounded up to the next thousandth, so that no side is longer than 14,400 units (ISO 32000-1, Annex C.2); in PDF 1.3 to 1.5 files and PDF/X files such a page is written in points.
     Placed (linked) files in a `.ai`'s editing data come in as linked images in their place, each showing the low-resolution preview the file keeps of it until its file is found or relinked in the Links panel (a file found next to the document or at its path is read as the document opens). A file with them no longer falls back to its PDF part, so its guides, sublayers and hidden objects open (#1264; `crates/eps/src/import/ai/tests.rs`, `crates/engine/src/tests/links.rs`). In a file opened that way, a gradient with stops in the middle runs its whole ramp across its shape and a gradient object no longer passes its fill to the next path (#1390); text objects with an appearance keep their own text and frame, type of hidden layers stays hidden, and type on later artboards lands on its text objects (#1391); area type whose frame is too short for a line of the fallback font shows its first line, the frame made taller with a warning in the open result (#1392).
     `.ai` and EPS editing-data import keeps template layers, and opens canvas and artboard ruler guides as ruler guides on their layers; guide objects stay editable guide paths (#779; `crates/eps/src/import/ai/tests.rs`, `crates/eps/src/import/tests_native.rs`).