fix: avoid Windows delay in voice settings

[tokito-99]

Summary

• Replaces the synchronous cmd /C ver process with an in-process Windows version query.
• Prevents the Tauri event loop from blocking when switching from Voice Input to Models.
• Adds regression tests for Windows compatibility detection.

Testing

• cargo fmt --check
• cargo test --manifest-path surfaces/gui/src-tauri/Cargo.toml voice_input_compatibility_tests
• cargo check --manifest-path surfaces/gui/src-tauri/Cargo.toml
• Manually verified on Windows that switching from Voice Input to Models no longer pauses.

Closes #163