get_project_problems returns empty array despite compilation errors in the project

## Description
The `get_project_problems` function consistently returns an empty array even when there are actual compilation errors in the project. This makes it impossible to programmatically retrieve project-wide errors through the MCP interface.

## Steps to Reproduce
1. Open a .NET project in JetBrains Rider
2. Introduce a compilation error (e.g., syntax error like `{v` instead of `{`)
3. Run build to confirm compilation errors exist
4. Call `get_project_problems` through MCP
5. Observe that it returns `[]` despite errors being visible in Rider's Problems view

## Expected Behavior
`get_project_problems` should return an array of compilation errors, warnings, and other issues detected in the project, similar to what's shown in Rider's Problems tool window.

## Actual Behavior
The function always returns an empty array `[]`, even after:
- Running project build
- Executing `InspectCode` action
- Waiting for IDE to update

## Workaround
Currently, the only way to detect errors is through a multi-step process:
1. Execute action `ReSharperGotoNextErrorInSolution` to navigate to a file with errors
2. Call `get_current_file_errors` to retrieve errors for the currently open file
3. Repeat to find all errors (not practical for large projects)

## Suggested Solutions
1. Fix `get_project_problems` to properly return all project issues
2. Add a new function `get_project_errors` specifically for compilation errors
3. Add optional parameters to `get_project_problems` to filter by severity or type

## Environment
- JetBrains Rider (with MCP proxy)
- Project type: .NET/C#
- MCP proxy version: @jetbrains/mcp-proxy (latest)

## Additional Context
The `get_current_file_errors` function works correctly and returns errors in the format:
```json
[{
"filePath": "Producer.cs",
"severity": "ERROR(400)",
"description": "Cannot resolve symbol 'v'",
"lineContent": " {v"
}]

It would be helpful if get_project_problems returned similar structured data for all project issues.