[C# Generator] CS0101: Type and child namespace share the same name when schema has nested sub-schema

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### What are you generating using Kiota, clients or plugins?

API Client/SDK

### In what context or format are you using Kiota?

Nuget tool

### Client library/SDK language

Csharp

### Describe the bug

[kiota-repro.zip](https://github.com/user-attachments/files/28167281/kiota-repro.zip)

When an OpenAPI spec defines a schema named Foo and a separate nested schema named Foo.Bar (dot-separated
component name), Kiota generates:

- Foo.cs → class Foo in namespace X.Y
- Foo/Bar.cs → namespace X.Y.Foo

C# does not allow a type and a child namespace to share the same identifier in the same scope, resulting in a
CS0101 compile error.

### Expected behavior

Kiota should detect this collision at generation time and either:
1. Rename the child namespace (e.g. ResourceTypeModels) to avoid the conflict, or
2. Emit a warning and suggest --exclude-path for the conflicting paths

### How to reproduce

Kiota version: 1.31.1
.NET version: 10.0.105
Language: CSharp

1. Download the attached internal_permission_service.openapi.json
2. Run:

kiota generate \
--language csharp \
--openapi internal_permission_service.openapi.json \
--output ./Generated \
--namespace-name My.Api \
--class-name InternalPermissionApiClient

3. Build the generated project

Generated output:

Generated/Models/Zitadel/Internal_permission/V2/
├── ResourceType.cs ← class ResourceType in namespace My.Api...V2
├── ResourceFilter.cs ← class ResourceFilter in namespace My.Api...V2
├── ResourceType/
│ └── ProjectGrant.cs ← namespace My.Api...V2.ResourceType ← CONFLICT
└── ResourceFilter/
└── ProjectGrant.cs ← namespace My.Api...V2.ResourceFilter ← CONFLICT

Compile error:

error CS0101: The namespace 'My.Api...V2' already contains a definition for 'ResourceType'
error CS0101: The namespace 'My.Api...V2' already contains a definition for 'ResourceFilter'

The spec contains component schemas ...ResourceType and ...ResourceType.ProjectGrant (dot-separated). Kiota
interprets the dot as a directory separator, generating a subdirectory ResourceType/ while also generating a class
file ResourceType.cs — causing the collision.

### Open API description file

[internal_permission_service.openapi.json](https://github.com/user-attachments/files/28167236/internal_permission_service.openapi.json)

### Kiota Version

1.31.1

### Latest Kiota version known to work for scenario above?(Not required)

_No response_

### Known Workarounds

_No response_

### Configuration

_No response_

### Debug output

Click to expand log
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### Other information

_No response_

Start with the attached internal_permission_service.openapi.json and reproduce the issue using the shown kiota generate command with --language csharp. Inspect how the C# generator maps dot-separated schemas into ResourceType.cs and ResourceType/ProjectGrant.cs, then build the generated output. Done means the conflicting schema produces valid C# without CS0101, with the chosen rename or warning behavior covered by a regression test.

Written by the indexing model from the issue text.