docs: add comprehensive doc comments, update keywords/categories, add badges

docs: add comprehensive doc comments, update keywords/categories, add badges

chore: update dependency versions in Cargo.lock

chore: bump version to 0.3.4

refactor: replace manual atomic write pattern with `atomic-write-file` crate

fix: gate directory fsync to Unix only for Windows compatibility

fix: add unsafe to extern block for Rust 2024 edition

fix: portable errno check and cfg-gate model2vec in struct

Merge pull request #1 from ramarivera/codex/fix-darwin-errno

fix: bump MSRV from 1.85 to 1.89

chore: refresh cache

ci: add cross-platform testing, MSRV, doc, and bench jobs

ci: replace Docker-based cargo-deny action with pre-built binary

fix(api): use portable unix errno lookup for liveness check

feat: switch default model to potion-base-32M and add --version flag