Revert "Overhaul shell detection and centralize command generation for unified exec" (#6606)

Reverts openai/codex#6577

codex-rs/core/src/command_safety/is_safe_command.rs

@@ -1,5 +1,4 @@
 use crate::bash::parse_shell_lc_plain_commands;
-use crate::command_safety::windows_safe_commands::is_safe_command_windows;
 
 pub fn is_known_safe_command(command: &[String]) -> bool {
     let command: Vec<String> = command
@@ -12,9 +11,12 @@ pub fn is_known_safe_command(command: &[String]) -> bool {
             }
         })
         .collect();
-
-    if is_safe_command_windows(&command) {
-        return true;
+    #[cfg(target_os = "windows")]
+    {
+        use super::windows_safe_commands::is_safe_command_windows;
+        if is_safe_command_windows(&command) {
+            return true;
+        }
     }
 
     if is_safe_to_call_with_exec(&command) {

codex-rs/core/src/command_safety/mod.rs

@@ -1,3 +1,4 @@
 pub mod is_dangerous_command;
 pub mod is_safe_command;
+#[cfg(target_os = "windows")]
 pub mod windows_safe_commands;