Resolves the 3 P3 items in docs/rewrite/notes/review-rv12-codex.md
(final-Z15.md):
- Sprite strokes: tiny-skia is replaced by a port of z2d 0.10's stroke
plotter (sprite/stroke.rs) plus z2d's arc segmentation and truncating
integer compositing, feeding the ported 4x4 multisample rasterizer.
All 36 reference sprite sheets now match Ghostty's byte for byte (test
tolerance 0), and `just visual-parity` with a production build shows
0 differing pixels (max delta 0) against the installed Ghostty 1.3.1
for the test page (block and bar cursor) and the tabs+splits scenario,
terminal area and chrome alike. tiny-skia dependency removed.
- zig_error maps errno values per target via libc (Linux, Darwin/BSD)
and Win32 codes the way Zig std does on Windows.
- theme=. / theme=.. report "it is a directory" via a port of
std.fs.path.basename, matching Ghostty.
Test Plan:
- cargo test --workspace --no-fail-fast (3498 passed, exit 0)
- cargo build --profile production && just visual-parity
- just check-macos (both), just check-windows, just check-wasm
