feat: implemented native ctok tokenization engine with model scopes

- Implemented the `ctok` Rust native tokenization engine with offline support for Claude V3, V47, V5, and V5Sonnet families.
- Replaced global token estimation with model-scoped `Tokenizer` instances and provider-anchored transcript accounting across packages.
- Added vocabulary generation scripts, test fixtures, and comprehensive unit tests for tokenizer routing and matching modes.

packages/natives/package.json

@@ -37,6 +37,7 @@
     "test": "bun test --parallel",
     "fix": "biome check --write --unsafe .",
     "fmt": "biome format --write .",
+    "gen:ctok": "bun scripts/gen-ctok-vocab.ts",
     "gen:native": "bun scripts/embed-native.ts",
     "gen:native:reset": "bun scripts/embed-native.ts --reset",
     "gen:npm": "bun scripts/gen-npm-packages.ts",