Replace `bincode` dependency: crate is unmaintained (poison-pill 3.0.0 release)

[Mec-iS]

Background

The bincode crate has been abandoned following a doxxing and harassment incident against its maintainer. A final 3.0.0 release was published to crates.io whose entire source is:

compile_error!("https://xkcd.com/2347/");

This intentionally breaks any project that upgrades to (or is bumped to) 3.0.0 — as seen in Dependabot PR for bincode-3.0.0. The crates.io page now reads:

Bincode is now unmaintained. Due to a doxxing and harassment incident, development on bincode has ceased. No further releases will be published on crates.io.

Current Impact

• Dependabot automatically opened a PR bumping bincode to 3.0.0, which fails to compile entirely.
• The serde feature test blocks in the following files are affected:
  • src/tree/decision_tree_regressor.rs
  • src/ensemble/random_forest_classifier.rs
  • src/ensemble/random_forest_regressor.rs

Proposed Solution

We should migrate away from bincode to an actively maintained alternative. The bincode maintainer themselves suggested the following options:

Crate	Notes
wincode	Drop-in bincode-compatible alternative
postcard	Similar in spirit to bincode, well-maintained, used in embedded/no_std contexts
rkyv	Zero-copy deserialization; excellent for intra-program message passing use cases like smartcore's serde tests

For smartcore's use case (serializing/deserializing trained models in tests), postcard or rkyv are likely the best fits. wincode is the lowest-friction migration if a drop-in replacement is preferred.

Short-term Workaround

Pin bincode back to 1.3.3 in Cargo.toml (the last stable, working release) while the migration is evaluated:

[dev-dependencies]
bincode = "=1.3.3"

Next Steps

• Decide on replacement crate
• Update Cargo.toml [dev-dependencies]
• Update serde test blocks in all three affected files
• Ensure wasm32 target continues to work (--target wasm32-unknown-unknown --all-features)