chore(plugin-openapi): add lint target and remove explicit any in specs (Fixes #54)

[michaelbe812]

Summary

• Add Nx lint target to plugin-openapi.
• Remove explicit any from specs using unknown and type aliases.
• Refactor build-command to avoid any in option access.

Details

• Enables nx run plugin-openapi:lint and surfaces lint warnings/errors for the package.
• Tests updated to use safer typing; behavior unchanged (all tests passing).

Why

• Keep codebase consistent and enforce linting for plugin-openapi.
• Address no-explicit-any in specs to improve type safety.

Verification

• nx run plugin-openapi:lint passes (only warnings for non-null assertions).
• nx run-many -t test passes across all projects.