[BUG][scala-sttp4] A schema named Request shadows sttp.client4.Request and the generated client does not compile

[vivekmahajan]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

If a spec declares a schema named Request, the generated scala-sttp4 client does not compile.

Every generated API imports its models explicitly and then wildcard-imports sttp:

import org.openapitools.client.model.Request
import sttp.client4._

In Scala an explicit import has higher precedence than a wildcard import, regardless of order, so Request resolves to the model. The operation's return type is emitted unqualified as Request[...], which then fails:

error: org.openapitools.client.model.Request does not take type parameters
  def predict(request: Request): Request[Either[ResponseException[String], Response]] =
                                 ^

Request is a common schema name for RPC-style APIs, so this is easy to hit.

The scala-sttp (sttp3) generator emits the qualified form sttp.client3.Request[..., Any] and is unaffected.

openapi-generator version

7.25.0-SNAPSHOT (current master).

OpenAPI declaration file content or url

openapi: 3.0.0
info:
  title: sttp4 model named Request
  version: 1.0.0
paths:
  /predict:
    post:
      operationId: predict
      requestBody:
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/Request'
      responses:
        '200':
          description: OK
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Response'
components:
  schemas:
    Request:
      type: object
      required: [userId]
      properties:
        userId: {type: string}
    Response:
      type: object
      properties:
        score: {type: number}

Generation Details

java -jar openapi-generator-cli.jar generate -g scala-sttp4 -i spec.yaml -o out

Steps to reproduce

1. Generate with the command above.
2. sbt compile in the output directory.
3. Compilation fails with Request does not take type parameters.

Suggest a fix

Qualify the return type in api.mustache as sttp.client4.Request[...], matching what scala-sttp already does.