feat(openapi): implement openapi toolset and integration tests (part 4)

[AmaadMartin]

Link to Issue or Description of Change

Problem:
To achieve parity with Python and fully automate OpenAPI integration, developers need a top-level BaseToolset that instantiates all individual tool endpoints from a spec file.

Solution:
Implemented OpenAPIToolset and integration tests (Part 4 of 4):

• openapi_toolset.ts: Accepts YAML/JSON specifications or raw documents, invokes the spec parser, and exposes generated RestApiTool instances.
• Adds test fixtures (petstore.yaml, truanon.yaml) and full integration tests.

Testing Plan

Unit Tests:

• I have added or updated unit tests for my change.
• All unit tests pass locally.

Summary of passed results:

• Achieved 95.14% overall test coverage across the complete OpenAPI toolset feature.
• Actual Line Coverage by File:
  • openapi_toolset.ts: 93.58%

Integration Tests:

• All integration tests pass locally.
• Verified that OpenAPIToolset successfully parses real-world specs and executes operations with mocked network requests.

Checklist

• I have performed a self-review of my own code.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.