feat: inline validators in standalone output

[RelevantShannon]

Add an opt-in mode that embeds Ajv's generated validators into fast-json-stringify standalone output.

Standalone mode currently restores an Ajv-backed validator from serialized schema state. Schemas using anyOf, oneOf, or if/then/else therefore still compile their branch validators at runtime. The new inlineValidators option asks Ajv's standalone compiler for the exact fragment validators used by the generated serializer and includes them in the same output module.

The inline path is intentionally scoped:

• it is only enabled for standalone mode when inlineValidators is true
• only schema fragments referenced by generated validator calls are emitted
• schemas that do not use Ajv-backed branches emit no validator code
• omitting or disabling the option preserves the existing state-restoration path
• generated validator code is forced to CommonJS while other caller-provided Ajv code options are preserved

This also makes the internal fjs_type keyword code-generating so Date and other toJSON values remain compatible with Ajv standalone output. External schema refs and built-in formats are included through Ajv's normal standalone dependency handling.

The output remains one generated module, but still uses fast-json-stringify's standalone serializer dependency and may reference small Ajv runtime helpers when required by the generated validation code.

Verification:

• npm run lint
• git diff --check
• node --test test/standalone-mode.test.js
• npm test

npm test passed locally with 479 tests and 0 failures.

[mcollina]

This is awesome. Why is it still a draft?

[RelevantShannon]

This is awesome. Why is it still a draft?

Ah sorry, it was a Friday, and I wasn't sure if it was ready yet. I think it is :D