feat(openapi-typescript): map OpenAPI int64 formats to bigint

[umbrik]

Changes

This PR updates openapi-typescript to map OpenAPI format: int64 values to TypeScript bigint instead of number.

• Added a shared BIGINT TypeScript AST keyword node.
• Updated schema transformation logic so type: integer/type: number with format: int64 emit bigint.
• Added/updated tests to cover:
  • integer + int32 → number
  • integer + int64 → bigint
  • number + int64 → bigint
  • nullable int64 cases → bigint | null
  • path parameter snapshots affected by int64
• Regenerated examples to reflect new int64 output (e.g. IDs now appear as bigint).

Related issue(s): N/A

How to Review

• Review the core transformation change for numeric schemas with format: int64.
• Review added test cases for number/integer format handling and nullable behavior.
• Verify updated snapshots/examples are consistent with expected int64 → bigint behavior.
• Optional local verification:
  • pnpm --filter openapi-typescript test

Checklist

• Unit tests updated
• docs updated
• pnpm run update:examples run (only applicable for openapi-typescript)

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[changeset-bot]

🦋 Changeset detected

Latest commit: c7ae01c

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
openapi-typescript	Minor

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