Resolves the parity items of docs/rewrite/notes/review-rv15-codex.md
(final-Z18.md):
- os::open inherits stdin like Zig's Child.init, strips LD_LIBRARY_PATH
only in Snap builds (new `snap` cargo feature, off by default, like
Zig's snap build option) and bounds output collection to 50 KiB per
stream (StdoutStreamTooLong/StderrStreamTooLong).
- +show-face writes diagnostics and lookup lines in the exact fragments
Zig's formatter produces, so buffer drains happen at the same byte
positions (0 diffs vs /usr/bin/ghostty over 0-44 bad options for
three codepoints); its tests no longer parse the test runner's argv.
- DEVIANT_FIXES.md: five entries reworded and four removed that were no
longer deviations (verified against code and oracle).
Test Plan:
- cargo test -p ghostty-os open; cargo test -p ghostty-cli show_face
Adds docs/rewrite/DEVIANT_FIXES.md, the single list of places where the
Rust port deliberately behaves differently from Ghostty 1.3.1:
- 30 upstream bugs fixed instead of replicated (memory safety/UB,
infinite loops, crashes, data loss), each with Zig file:line, both
behaviours, the commit that introduced the Rust behaviour and its test
(a few Zig locations are marked unverified);
- 11 upstream quirks deliberately kept as in Zig;
- 18 other deliberate deviations (out-of-scope Swift app, platforms that
are only compile-checked, library substitutions with observable
differences).
Deviations made from now on are committed alone as fix-deviant(<scope>)
and added here; earlier ones are bundled in larger commits, which is why
the register records their hashes.