Report an error when trying to open ui in linux::headless (#11952)

Release Notes:

- N/A

crates/gpui/src/platform/linux/headless/client.rs

@@ -68,6 +68,10 @@ impl LinuxClient for HeadlessClient {
         None
     }
 
+    fn can_open_windows(&self) -> anyhow::Result<()> {
+        return Err(anyhow::anyhow!("neither DISPLAY, nor WAYLAND_DISPLAY found. You can still run zed for remote development with --dev-server-token."));
+    }
+
     fn open_window(
         &self,
         _handle: AnyWindowHandle,

crates/gpui/src/platform/linux/platform.rs

@@ -55,6 +55,9 @@ pub trait LinuxClient {
     fn displays(&self) -> Vec<Rc<dyn PlatformDisplay>>;
     fn primary_display(&self) -> Option<Rc<dyn PlatformDisplay>>;
     fn display(&self, id: DisplayId) -> Option<Rc<dyn PlatformDisplay>>;
+    fn can_open_windows(&self) -> anyhow::Result<()> {
+        Ok(())
+    }
     fn open_window(
         &self,
         handle: AnyWindowHandle,
@@ -132,6 +135,10 @@ impl<P: LinuxClient + 'static> Platform for P {
         });
     }
 
+    fn can_open_windows(&self) -> anyhow::Result<()> {
+        self.can_open_windows()
+    }
+
     fn quit(&self) {
         self.with_common(|common| common.signal.stop());
     }