[ruby-nextgen] Expose nested resources through clients

[axelray-dev]

Fixes #24999

Summary

Expose nested Ruby-nextgen resource clients through their namespace clients. This makes paths such as client.store.order available to callers and also generates a concrete namespace class when a namespace only contains nested resources, so Zeitwerk can load the generated files correctly.

The change adds regression coverage for direct and namespace-only nested resources, including multiple child resources, and updates the Petstore sample to expose client.store.order.

Validation

• CircleCI node0 through node3 passed.
• git diff --check passed.
• The focused Maven test could not run on the VPS because Java is not installed; the generator test suite is covered by CI.

[cubic-dev-ai]

All reported issues were addressed across 7 files

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[cubic-dev-ai]

All reported issues were addressed across 1 file (changes from recent commits).

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[axelray-dev]

Addressed the current review findings in a445f4a. Namespace-only output now follows the first actually generated nested resource, resource accessors avoid initialize and direct-operation collisions, and generated metadata continues to derive from the processed operation set. git diff --check passed on the VPS; Java and Maven are not installed there, so CI is the authoritative generator test. Please re-review the new head.

[wing328]

thanks for the PR. please review the build failure when you've time.

cc @n-rodriguez (author of ruby-nextgen)

[axelray-dev]

Addressed the build failure in e52ac91. The RubyNextgenClientCodegenTest suite now passes 21/21 on the VPS. Resource filename basenames are kept separate from collision-safe client accessors for Zeitwerk inflections, the acronym assertion now matches the namespace-only generated layout, and the nested-resource test now covers the namespace client accessor. Please re-review the new head.

[wing328]

https://github.com/OpenAPITools/openapi-generator/actions/runs/36342013652/job/108827995027?pr=25002

please update the samples to fix the CI failure.