[Initiative] Detection Engine OpenAPI cleanup

[yctercero]

Problem statement

The Kibana OAS spec is incomplete. There are missing examples and missing descriptions across many API routes.

The OpenAPI Specification serves as a standardized, machine-readable contract that automatically generates interactive documentation for humans and provides the structural roadmap necessary for AI agents to autonomously discover, understand, and execute API calls.

Examples and descriptions are critical because they provide the semantic context and data patterns required for humans to understand intent and for agents to accurately map parameters, preventing hallucinated inputs and integration failures.

Poor or missing examples/descriptions lead to substandard outcomes for agents and users that are interacting with Kibana.

[elasticmachine]

Pinging @elastic/security-detection-engine (Team:Detection Engine)