Function merge_linked_http 

pub fn merge_linked_http(base: ApiOpenApiRouter) -> ApiOpenApiRouter

Merge every linked module’s HTTP routes (and their OpenAPI docs) onto base.

Linked route builders are context-free, so this assembles the HTTP surface without constructing the full module set (which requires an AppContext) — usable both for serving and for standalone OpenAPI document assembly. This is the single source for linked API routes until HTTP joins the platform_module::ModuleBinding seam.