Add support for OpenApi best practices

[jabrena]

User story

As a maintainer or consumer of Java-centric AI rules and agent skills for API design,
I want a dedicated, framework-agnostic OpenAPI guidance package under the 701 prefix (701-technologies-openapi),
so that agents can apply consistent contract design, versioning, documentation, validation, and codegen practices without coupling to Spring Boot, Quarkus, or Micronaut specifics.

Scope

Introduce the 700–799 “technologies” band (starting with 701) for cross-cutting API contract guidance. 701-technologies-openapi complements existing framework REST skills (302, 402, 502), which already mention OpenAPI in a framework context, by focusing on OpenAPI/Swagger as the artifact: spec structure, metadata, paths/schemas, security schemes, examples, linting (e.g. Spectral), breaking-change awareness, and alignment with OpenAPI 3.x best practices.

Deliverables (implementation checklist)

• skills-generator/src/main/resources/system-prompts/701-technologies-openapi.xml — PML system prompt (per pml.xsd)
• skills-generator/src/main/resources/skills/701-skill.xml — matching agent skill (id="701-technologies-openapi")
• Register 701 in skills-generator/src/main/resources/skill-inventory.json and system-prompt-inventory.json
• Run ./mvnw clean verify -pl skills-generator (and full verify as appropriate); regenerate skills via ./mvnw clean install -pl skills-generator
• 700 band convention: document in contributor docs that 701+ is reserved for technology-focused prompts (OpenAPI first); avoid reusing Spring/Quarkus/Micronaut 3xx/4xx/5xx prefixes for this work

Acceptance criteria

1. Given a repo change that adds OpenAPI guidance, when the new XML sources are merged, then skills-generator builds successfully and generated outputs include the new 701 skill.
2. Given an agent triggered for “OpenAPI best practices” without a named framework, when the skill is selected, then recommendations are framework-agnostic (spec quality, lifecycle, validation, codegen handoffs) and explicitly defer framework wiring to 302 / 402 / 502 where relevant.
3. Given the inventory files, when contributors search for OpenAPI-related skills, then 701 appears with a clear description and distinct triggers from fuzzing (134) and REST framework skills.

Notes

• Related issue title: OpenAPI best practices for the java-cursor-rules / cursor-rules-java skills family.
• Optional follow-up: OpenSpec change under documentation/openspec/changes/ if the maintainers want a formal proposal before large XML authoring.

[jabrena]

#635