[jiggy-techy]

Summary

Adds explicit cross-platform and endianness coverage.

• crates/devkit-xdr/tests/endianness.rs pins XDR's big-endian wire format with explicit byte arrays for ScVal::U32, ScVal::I32, and ScVal::I64, round-trips them, and asserts host-independent base64/JSON output.
• crates/devkit-core/tests/cross_platform.rs asserts that native and forward-slash paths produce identical components, that interior . components are removed, and that parsers accept CRLF input.
• crates/devkit-cli/tests/path_normalization.rs runs inspect-wasm with a native path, a forward-slash path, and a path containing .., requiring byte-identical JSON output.
• Documents the strategy in docs/TESTING.md and CHANGELOG.md.

Verification

cargo fmt --all -- --check
cargo clippy --all-targets --all-features -- -D warnings
cargo test --all

All pass locally (Windows). The added tests use explicit bytes and path components, so they are also valid on the Linux and macOS CI runners.

Closes #91