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/derive.rs

@@ -0,0 +1,77 @@
+#![cfg(feature = "derive")]
+#![allow(dead_code)]
+
+use bytemuck::{ByteEq, ByteHash, Pod, TransparentWrapper, Zeroable};
+use std::marker::PhantomData;
+
+#[derive(Copy, Clone, Pod, Zeroable, ByteEq, ByteHash)]
+#[repr(C)]
+struct Test {
+  a: u16,
+  b: u16,
+}
+
+#[derive(TransparentWrapper)]
+#[repr(transparent)]
+struct TransparentSingle {
+  a: u16,
+}
+
+#[derive(TransparentWrapper)]
+#[repr(transparent)]
+#[transparent(u16)]
+struct TransparentWithZeroSized {
+  a: u16,
+  b: (),
+}
+
+#[derive(TransparentWrapper)]
+#[repr(transparent)]
+struct TransparentWithGeneric<T: ?Sized> {
+  a: T,
+}
+
+/// Ensuring that no additional bounds are emitted.
+/// See https://github.com/Lokathor/bytemuck/issues/145
+fn test_generic<T>(x: T) -> TransparentWithGeneric<T> {
+  TransparentWithGeneric::wrap(x)
+}
+
+#[derive(TransparentWrapper)]
+#[repr(transparent)]
+#[transparent(T)]
+struct TransparentWithGenericAndZeroSized<T: ?Sized> {
+  a: (),
+  b: T,
+}
+
+/// Ensuring that no additional bounds are emitted.
+/// See https://github.com/Lokathor/bytemuck/issues/145
+fn test_generic_with_zst<T>(x: T) -> TransparentWithGenericAndZeroSized<T> {
+  TransparentWithGenericAndZeroSized::wrap(x)
+}
+
+#[derive(TransparentWrapper)]
+#[repr(transparent)]
+struct TransparentUnsized {
+  a: dyn std::fmt::Debug,
+}
+
+type DynDebug = dyn std::fmt::Debug;
+
+#[derive(TransparentWrapper)]
+#[repr(transparent)]
+#[transparent(DynDebug)]
+struct TransparentUnsizedWithZeroSized {
+  a: (),
+  b: DynDebug,
+}
+
+#[derive(TransparentWrapper)]
+#[repr(transparent)]
+#[transparent(DynDebug)]
+struct TransparentUnsizedWithGenericZeroSizeds<T: ?Sized, U: ?Sized> {
+  a: PhantomData<T>,
+  b: PhantomData<U>,
+  c: DynDebug,
+}