feat(sandbox): implement cross-platform support with Windows fallback

- Add conditional compilation for Unix-specific gaol sandbox functionality
- Implement Windows-compatible SandboxExecutor with no-op sandboxing
- Update ProfileBuilder to handle both Unix and Windows platforms
- Add platform-specific dependency declaration for gaol crate
- Modify agent and claude commands to use appropriate sandbox implementation
- Update test modules with conditional compilation for Unix-only tests
- Ensure graceful degradation on Windows with logging warnings

This change enables the application to build and run on Windows while
maintaining full sandbox security on Unix-like systems.

src-tauri/tests/sandbox/mod.rs

@@ -2,8 +2,16 @@
 //! 
 //! This test suite validates the sandboxing capabilities across different platforms,
 //! ensuring that security policies are correctly enforced.
+
+#[cfg(unix)]
 #[macro_use]
 pub mod common;
+
+#[cfg(unix)]
 pub mod unit;
+
+#[cfg(unix)]
 pub mod integration;
+
+#[cfg(unix)]
 pub mod e2e;