internity v0.1.0

Initial release.

Added

• LocalLexicon — a fast, single-threaded string interner (&mut self interning,
  live &self resolution).
• ThreadedLexicon — a concurrent string interner: &self interning from many
  threads, a cheap Clone Arc-backed handle, fill-then-freeze.
• Sym — a 4-byte, Copy, niche-optimized handle; as_u32/from_u32 and
  From<Sym> for u32 conversions; iter() over (Sym, &str).
• Reader — a sealed trait for the frozen, Send + Sync, lock-free read form,
  produced by LocalLexicon::freeze / ThreadedLexicon::freeze; supports iter().
• SymMap / SymSet / SymBuildHasher — fast Sym-keyed maps and sets via an
  identity-style hasher.
• Extend and FromIterator for both interners.
• Generic over the BuildHasher, defaulting to a fast non-cryptographic hasher.
• no_std support: the crate is no_std + alloc without the default std
  feature (which enables ThreadedLexicon).
• Optional serde feature: a string-based, interner-aware serialization model.
  #[derive(SerializeIn)] / #[derive(DeserializeIn)] resolve each Sym
  against a Reader / interner so values round-trip as their strings
  (serialize a Sym to its string, deserialize a string back into a Sym),
  making corpora portable across processes. SerializeReader snapshots a whole
  frozen corpus. Sym itself has no plain Serialize/Deserialize (a raw
  handle is meaningless outside its lexicon), and the live ThreadedLexicon is
  deserialize-only — serialize the frozen Reader instead.