fix: resolve refs to definitions keys with percent-encoded characters - #871

Fixes #740.

Problem

When a definitions (or ``) key contains percent-encoded characters (e.g. 'Some%3Cloremipsum%3E') and its subschema uses `oneOf`/`allOf`/`anyOf`, building fails with `can't resolve reference` from ajv.

Root cause: the two resolvers disagree on how to interpret the fragment. ajv (per the JSON Schema spec) percent-decodes the fragment before looking up the definitions key (`unescapeFragment` = `decodeURIComponent` + JSON-pointer unescape), while the internal serializer resolves refs literally. A key copied verbatim into matches on the serializer side but misses on the ajv side.

Solution

In Validator.convertSchemaToAjvFormat, percent-decode the definitions/`` keys before handing the schema to ajv, so both resolvers agree:

• invalid/incomplete percent sequences are decoded segment-by-segment, leaving invalid segments untouched
• a key whose decoded form would collide with an existing key is left untouched
• getState() now stores the converted schema, so the standalone-mode validator sees the same normalized keys

Tests

Added two tests in test/ref.test.js: a definitions key with %3C/%3E plus oneOf, and a `` variant. Full suite passes (493 tests), types (12 assertions) and eslint clean.