feat: add display UI with splash screen, dashboard, and RSSI sparkline

Implement full SSD1306 OLED display support:
- Splash screen on boot (1.5s) with project name, version, board
- Dashboard showing radio state, config, counters, RSSI/SNR
- RSSI history sparkline (64-sample ring buffer, 2px-wide bars)
- DisplayOn/DisplayOff host commands routed via dedicated channel
- Pure render functions against generic DrawTarget (no hardware coupling)
- Display on/off control bypasses radio task entirely

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/bytemuck/tests/transparent.rs

@@ -0,0 +1,116 @@
+// Currently this test doesn't actually check the output of the functions.
+// It's only here for miri to check for any potential undefined behaviour.
+// TODO: check function results
+
+#[test]
+fn test_transparent_wrapper() {
+  // An external type defined in a different crate.
+  #[derive(Debug, Copy, Clone, Default)]
+  struct Foreign(u8);
+
+  use bytemuck::TransparentWrapper;
+
+  #[derive(Debug, Copy, Clone)]
+  #[repr(transparent)]
+  struct Wrapper(Foreign);
+
+  unsafe impl TransparentWrapper<Foreign> for Wrapper {}
+
+  // Traits can be implemented on crate-local wrapper.
+  unsafe impl bytemuck::Zeroable for Wrapper {}
+  unsafe impl bytemuck::Pod for Wrapper {}
+
+  impl PartialEq<u8> for Foreign {
+    fn eq(&self, &other: &u8) -> bool {
+      self.0 == other
+    }
+  }
+
+  impl PartialEq<u8> for Wrapper {
+    fn eq(&self, &other: &u8) -> bool {
+      self.0 == other
+    }
+  }
+
+  let _: u8 = bytemuck::cast(Wrapper::wrap(Foreign::default()));
+  let _: Foreign = Wrapper::peel(bytemuck::cast(u8::default()));
+
+  let _: &u8 = bytemuck::cast_ref(Wrapper::wrap_ref(&Foreign::default()));
+  let _: &Foreign = Wrapper::peel_ref(bytemuck::cast_ref(&u8::default()));
+
+  let _: &mut u8 =
+    bytemuck::cast_mut(Wrapper::wrap_mut(&mut Foreign::default()));
+  let _: &mut Foreign =
+    Wrapper::peel_mut(bytemuck::cast_mut(&mut u8::default()));
+
+  let _: &[u8] =
+    bytemuck::cast_slice(Wrapper::wrap_slice(&[Foreign::default()]));
+  let _: &[Foreign] =
+    Wrapper::peel_slice(bytemuck::cast_slice(&[u8::default()]));
+
+  let _: &mut [u8] =
+    bytemuck::cast_slice_mut(Wrapper::wrap_slice_mut(
+      &mut [Foreign::default()],
+    ));
+  let _: &mut [Foreign] =
+    Wrapper::peel_slice_mut(bytemuck::cast_slice_mut(&mut [u8::default()]));
+
+  let _: &[u8] = bytemuck::bytes_of(Wrapper::wrap_ref(&Foreign::default()));
+  let _: &Foreign = Wrapper::peel_ref(bytemuck::from_bytes(&[u8::default()]));
+
+  let _: &mut [u8] =
+    bytemuck::bytes_of_mut(Wrapper::wrap_mut(&mut Foreign::default()));
+  let _: &mut Foreign =
+    Wrapper::peel_mut(bytemuck::from_bytes_mut(&mut [u8::default()]));
+
+  // not sure if this is the right usage
+  let _ =
+    bytemuck::pod_align_to::<_, u8>(Wrapper::wrap_slice(&[Foreign::default()]));
+  // counterpart?
+
+  // not sure if this is the right usage
+  let _ = bytemuck::pod_align_to_mut::<_, u8>(Wrapper::wrap_slice_mut(&mut [
+    Foreign::default(),
+  ]));
+  // counterpart?
+
+  #[cfg(feature = "extern_crate_alloc")]
+  {
+    use bytemuck::allocation::TransparentWrapperAlloc;
+    use std::rc::Rc;
+
+    let a: Vec<Foreign> = vec![Foreign::default(); 2];
+
+    let b: Vec<Wrapper> = Wrapper::wrap_vec(a);
+    assert_eq!(b, [0, 0]);
+
+    let c: Vec<Foreign> = Wrapper::peel_vec(b);
+    assert_eq!(c, [0, 0]);
+
+    let d: Box<Foreign> = Box::new(Foreign::default());
+
+    let e: Box<Wrapper> = Wrapper::wrap_box(d);
+    assert_eq!(&*e, &0);
+    let f: Box<Foreign> = Wrapper::peel_box(e);
+    assert_eq!(&*f, &0);
+
+    let g: Rc<Foreign> = Rc::new(Foreign::default());
+
+    let h: Rc<Wrapper> = Wrapper::wrap_rc(g);
+    assert_eq!(&*h, &0);
+    let i: Rc<Foreign> = Wrapper::peel_rc(h);
+    assert_eq!(&*i, &0);
+
+    #[cfg(target_has_atomic = "ptr")]
+    {
+      use std::sync::Arc;
+
+      let j: Arc<Foreign> = Arc::new(Foreign::default());
+
+      let k: Arc<Wrapper> = Wrapper::wrap_arc(j);
+      assert_eq!(&*k, &0);
+      let l: Arc<Foreign> = Wrapper::peel_arc(k);
+      assert_eq!(&*l, &0);
+    }
+  }
+}