refactor JSON tokenizer state

[bobzhang]

What changed

• add a private JsonState enum for normal and block-comment modes
• carry the typed state through the JSON lexer loop
• confine the existing TokenizerState("n") / TokenizerState("c") representation to encode/decode boundary helpers
• preserve unknown-state fallback behavior and the public tokenizer API

Why

This isolates JSON's language-specific state semantics from the shared, language-neutral TokenizerState carrier. It provides a small prototype for evaluating a typed state representation without committing the public API to a closed cross-language enum.

Validation

• JSON lexer checks with warning 73 enabled on JS, native, and Wasm
• JSON lexer tests: 8/8 on JS, native, and Wasm
• complete editor suite: 1,023/1,023 tests
• moon info: no public API change

The root just check, just test, and just build gates cannot resolve this checkout because the workspace member desktop/lepus/config is absent; they fail before compiling the change.