fix: improve error handling and code robustness

- state_machine.rs: if-let replaces is_some()+take().unwrap()
- state_machine.rs: expect() replaces unwrap() with invariant docs
- wifi/mod.rs: send_result uses self.id() instead of hardcoded string

src/plugins/wifi/mod.rs

@@ -111,7 +111,7 @@ impl WifiPlugin {
             .context("wifi plugin context is not initialized")?;
 
         ctx.tx.send(Envelope {
-            from: "wifi".to_string(),
+            from: self.id().to_string(),
             to: Destination::Broadcast,
             message: Message::WifiResult(payload),
         })?;