Complete OpenAPI documentation support

[rtcoder]

Changes

• Add OpenAPI documentation attributes: Summary, Description, Tag, Response, Deprecated, Security, and Schema.
• Extend OpenAPI generation with summaries, descriptions, custom tags, custom responses, security metadata, deprecation metadata, formats, enums, nullable fields, and required fields.
• Add ./shift openapi --validate and use it from ./shift qa.
• Add an OpenAPI validator for required document fields, unique operation ids, responses, and path parameters.
• Improve the live OpenAPI viewer with endpoint search, tag filtering, dark mode, operation counts, security display, and JSON download.
• Document OpenAPI attributes and validation in README, docs/index.html, and REFACTORING.md.
• Add tests for OpenAPI attributes, validator behavior, live page controls, and validate help output.

Verification

• composer test
• ./shift lint
• ./shift qa
• ./shift openapi
• ./shift openapi --validate
• ./shift openapi --live --port=8099 with HTTP checks for / and /openapi.json
• ./shift help openapi
• Documentation anchor check for all in-page navigation links

Release

• Version label: v0.22.1