fix: handle PowerShell ENOENT error in os-name on Windows

[roomote]

This PR attempts to address Issue #9859. Feedback and guidance are welcome.

Problem

Users on Windows without PowerShell in their PATH were experiencing API request failures with the error:

Command failed with ENOENT: powershell (Get-CimInstance -ClassName Win32_OperatingSystem).caption
spawnSync powershell ENOENT

Solution

Added error handling around the osName() call in system-info.ts to gracefully handle cases where PowerShell is not available:

• Wrapped osName() in a try-catch block
• Provides a fallback using Node's built-in os.platform() and os.release() when osName() fails
• Ensures the application continues to work regardless of PowerShell availability

Changes

• Modified src/core/prompts/sections/system-info.ts to add error handling
• Added comprehensive tests in src/core/prompts/sections/__tests__/system-info.spec.ts

Testing

• Added unit tests covering both success and error scenarios
• Tests verify the fallback mechanism works correctly when PowerShell is not available
• All tests pass successfully

Fixes #9859

[roomote]

Rooviewer   See task on Roo Cloud

Re-reviewed the PR. The previous issue has been resolved.

• Remove redundant String.prototype.toPosix setup/teardown in test file (already provided globally by vitest setup)

Previous reviews

• 0284a3c: Review #1

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[roomote]

Fixaroo   See task on Roo Cloud

Fixed the reported issue. All local checks passed.

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