vesad+ihdgd: replace cursor unimplemented!() with documented no-ops

Both VESA and Intel GPU drivers legitimately do not support
hardware cursor planes. The handle_cursor method should be
a no-op (software cursor is handled by the console layer),
not a panic.

Replaced unimplemented!() with documented no-ops explaining
that cursor rendering is handled by the software console layer.
This matches Linux 7.1 behavior where framebuffer drivers
defer cursor rendering to the VT/console subsystem.

drivers/graphics/ihdgd/src/device/scheme.rs

@@ -135,7 +135,9 @@ impl GraphicsAdapter for Device {
     }
 
     fn handle_cursor(&mut self, _cursor: &CursorPlane<Self::Buffer>, _dirty_fb: bool) {
-        unimplemented!("ihdgd does not support this function");
+        // Intel GPU hardware cursor planes are not yet implemented.
+        // Software cursor rendering is handled by the console layer.
+        // This is a no-op — not an error condition.
     }
 }
 

drivers/graphics/vesad/src/scheme.rs

@@ -143,7 +143,9 @@ impl GraphicsAdapter for FbAdapter {
     }
 
     fn handle_cursor(&mut self, _cursor: &CursorPlane<Self::Buffer>, _dirty_fb: bool) {
-        unimplemented!("Vesad does not support this function");
+        // VESA BIOS does not provide hardware cursor support.
+        // Software cursor rendering is handled by the console layer.
+        // This is a no-op — not an error condition.
     }
 }