Mock setup extensions fail to compile for parameters named matchers or mock #7657

Summary

Mocking an interface whose method has a parameter named matchers or mock produces conflicting identifiers in generated setup extensions. Valid interface parameter names should compile with Mock.Of<T>().

Reproduction

In a project using TUnit.Mocks, define:

public interface IService
{
    void Send(string matchers);
    void Receive(string mock);
}

Generate a mock with Mock.Of<IService>() and build.

Expected and actual

Expected: generated setup extensions use distinct identifiers and compile.
Actual: setup extensions copy parameter names but also declare a local matchers and a receiver parameter mock, causing duplicate declarations. The predicate-local allocator in #7655 addresses a separate collision and does not fix these fixed names.

Environment

Observed in generated setup extensions at commit 07f7cd9, src/TUnit.Mocks.SourceGenerator/Builders/MockMembersBuilder.cs, in review of #7655. The checked-in snapshot in that PR shows the fixed receiver and local declarations.

Please allocate generated receiver and local names without colliding with source parameter names, with compilation regression coverage.