fix: resolve compilation errors in uuproc tests and add Windows dependencies

- Fix E0425 errors in test_uuproc.rs by removing leading underscores from variable names
  - Line 464: _empty_cmdline -> empty_cmdline (used in Linux-specific assertion)
  - Line 640: _processes -> processes (used in Linux-specific assertion)

- Add missing winapi dependency for Windows platform
  - Add winapi 0.3 with tlhelp32 and minwindef features to Cargo.toml
  - Resolves E0433 errors for unresolved winapi imports in windows.rs

Author: naoNao89

Cargo.lock

@@ -26,7 +26,7 @@ libc = { workspace = true }
 # macOS-specific dependencies can be added here
 
 [target.'cfg(target_os = "windows")'.dependencies]
-# Windows-specific dependencies can be added here
+winapi = { version = "0.3", features = ["tlhelp32", "minwindef"] }
 
 [lib]
 path = "src/lib.rs"

src/uu/uuproc/Cargo.toml

@@ -461,7 +461,7 @@ fn test_walk_process_handles_process_with_no_cmdline() {
     // Some processes may have empty command lines (kernel threads)
     let processes: Vec<_> = walk_process().collect();
 
-    let _empty_cmdline: Vec<_> = processes.iter().filter(|p| p.cmdline.is_empty()).collect();
+    let empty_cmdline: Vec<_> = processes.iter().filter(|p| p.cmdline.is_empty()).collect();
 
     // On Linux, kernel threads have empty command lines
     #[cfg(target_os = "linux")]
@@ -637,7 +637,7 @@ fn test_windows_current_process_detection() {
 #[cfg(unix)]
 fn test_unix_process_hierarchy() {
     // Verify process hierarchy on Unix systems
-    let _processes: Vec<_> = walk_process().collect();
+    let processes: Vec<_> = walk_process().collect();
 
     // Should have init process (PID 1) on Unix
     #[cfg(target_os = "linux")]