feat: Improve service manager testing and error handling

- Add comprehensive testing instructions to README.
- Improve error handling in examples to prevent crashes.
- Enhance launchctl error handling for production safety.
- Improve zinit error handling for production safety.
- Remove obsolete plan_to_fix.md file.
- Update Rhai integration tests for improved robustness.
- Improve service manager creation on Linux with systemd fallback.

service_manager/src/rhai.rs

@@ -14,10 +14,12 @@ pub struct RhaiServiceManager {
 }
 
 impl RhaiServiceManager {
-    pub fn new() -> Self {
-        Self {
-            inner: Arc::new(create_service_manager()),
-        }
+    pub fn new() -> Result<Self, Box<EvalAltResult>> {
+        let manager = create_service_manager()
+            .map_err(|e| format!("Failed to create service manager: {}", e))?;
+        Ok(Self {
+            inner: Arc::new(manager),
+        })
     }
 }
 
@@ -25,7 +27,10 @@ impl RhaiServiceManager {
 pub fn register_service_manager_module(engine: &mut Engine) -> Result<(), Box<EvalAltResult>> {
     // Factory function to create service manager
     engine.register_type::<RhaiServiceManager>();
-    engine.register_fn("create_service_manager", RhaiServiceManager::new);
+    engine.register_fn(
+        "create_service_manager",
+        || -> Result<RhaiServiceManager, Box<EvalAltResult>> { RhaiServiceManager::new() },
+    );
 
     // Service management functions
     engine.register_fn(