docs.rs cannot build 0.6.1: skia-safe 0.82 is broken there

[LeadcodeDev]

rustmotion 0.6.1 published, but docs.rs could not build it:
https://docs.rs/crate/rustmotion/0.6.1/builds/4176083

Cause

skia-bindings 0.82.0 has a docs.rs-specific path in its build script, and it is
broken:

DETECTED DOCS_RS BUILD
COPYING bindings_docs.rs to OUT_DIR/skia/bindings.rs
Error: Os { code: 2, kind: NotFound, message: "No such file or directory" }

The build script exits 1, so rustdoc never runs.

This is upstream, not ours: skia-safe 0.82.0 has no documentation on docs.rs
either — its own build failed the same way. skia-safe 0.99.0 builds fine. The
fix is to move off 0.82.

Scope, measured rather than estimated

Bumping the three crates to skia-safe = "0.99" and running cargo check --workspace produces 30 errors, all of one kind: Skia made SkPath immutable
and moved construction into SkPathBuilder, so the mutating methods left Path.

// before
let mut p = Path::new();
p.move_to(a); p.line_to(b); p.close();
p

// after
let mut b = PathBuilder::new();
b.move_to(a); b.line_to(b); b.close();
b.detach()

PathBuilder exists in 0.99 with detach() and snapshot().

Affected call sites:

Crate	Files	Call sites
rustmotion-components	18	147
rustmotion-core	3	30
rustmotion	1	1
Total	22	178

rustmotion-html, rustmotion-studio and rustmotion-cli are untouched.

Of the 99 files that use skia_safe, only 22 break. Canvas, Paint, Surface,
ImageInfo, FontStyle, Shader and Data crossed seventeen minor versions
unchanged.

178 is a floor, not a total. Cargo stopped at rustmotion-core, so the two
downstream crates were never type-checked. Further breakage may exist in
rustmotion-components, and it cannot be seen until core compiles.

Verification

The pixel regression suite is the judge here, not the compiler: if the paths are
built the same way they render the same way, and the tests say so.