Library API: portable core crate with CLI and WASM adapters

[hypnagonia]

Turns the project into a proper Rust library, with the CLI and the WebAssembly bindings as thin adapters over it.

Layout

A Cargo workspace, so the dependency direction is enforced by crate boundaries:

Crate	Path	Role
eigentrust	src/	the library: plain rlib, builds on every target, no wasm gating
eigentrust-cli	cli/	the eigentrust binary; uses only the public API
eigentrust-wasm	wasm/	JS bindings, the only cdylib, publish = false

Public API

Everything is re-exported from lib.rs, and all modules are private.

use eigentrust::{eigentrust, eigentrust_with_options, EigenTrustOptions, PreTrust, TrustEdge};

let result = eigentrust([TrustEdge::new(0, 1, 2.0), TrustEdge::new(1, 0, 1.0)], [PreTrust::new(0, 1.0)])?;
result.scores(); result.ranking(); result.iterations(); result.residual();

• EigenTrustOptions: alpha, epsilon, max_iterations. Private fields with a builder, validated before any work.
• EigenTrustError is #[non_exhaustive], covering invalid options, non-finite, negative or overflowing weights, invalid peers, an empty network and non-convergence.
• Feature csv: csv::Network::from_csv, with its own error type (line numbers and kinds).
• Feature parallel: rayon. There are no default features.
• The input rules (weights, normalization, duplicates, α = 0, convergence) are documented in the crate docs.

Verification

• CLI output is byte-identical to main on 10 reference inputs (up to 5M lines), and the CLI is about 15% faster.
• WASM output is byte-identical, at the same speed in Node and in the browser with threads.
• 44 tests: unit, public-API integration tests (tests/api.rs, tests/csv.rs), and doc tests including the README example.
• Clippy is clean natively (all and no features) and on wasm32. Rustdoc builds with -D warnings as docs.rs does. cargo machete is clean.
• cargo package -p eigentrust -p eigentrust-cli builds from the tarballs. The library package is 26 KB of sources, tests, examples, test data and licenses.
• cargo-semver-checks runs against the base branch. It's informational until the first crates.io release, and I checked that it catches a removed method.

Removed

• The unused sparse helpers (CSC, merge, sorting utils).
• The distrust functions that were never wired in. Negative weights stay rejected.