Resolve the docs/parity.md conflict, keep the HEIC rows. `cargo xtask ci` gets
a heif step (clippy + tests for lightcraft-codecs with --features heif), since
the workspace build leaves the feature off. The Cargo.toml comments no longer
say official builds enable it; the web one notes that wasm32 aborts on panic.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>