fix: resolve nested remote schema references

[Himenon]

Summary

This pull request fixes Issue #90, where a schema referenced from a remote document could contain another local reference and cause a stack overflow during code generation.

Reference resolution now uses the document containing each reference as the base point, and traverses nested local and remote references across multiple documents. The regression scenario covers the following chain:

v1 → v0#/components/schemas/Book → v0#/components/schemas/BookIDAlias → v2#/components/schemas/BookID

The implementation also detects circular schema references and includes Japanese comments explaining the reference-resolution flow.

Test Plan

The change follows a two-commit TDD sequence:

1. 94cd890 adds only the Issue Bug: complex remote reference is broken #90 reproduction fixtures. CI failed as expected with RangeError: Maximum call stack size exceeded in findSchemaByPathArray.
2. 6989bd0 adds the implementation, regression tests, complex chained-reference fixtures, and updated snapshots.

Verification:

• pnpm test passes: 43 unit tests and 55 snapshot tests.
• Type checking and Biome checks pass.
• GitHub Actions Build passes on Ubuntu and Windows.

Closes #90