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/zerocopy-derive/tests/ui/derive_transparent.rs

@@ -0,0 +1,48 @@
+// Copyright 2019 The Fuchsia Authors
+//
+// Licensed under a BSD-style license <LICENSE-BSD>, Apache License, Version 2.0
+// <LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0>, or the MIT
+// license <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your option.
+// This file may not be copied, modified, or distributed except according to
+// those terms.
+
+extern crate zerocopy_renamed;
+
+#[path = "../include.rs"]
+mod util;
+
+use core::marker::PhantomData;
+
+use zerocopy_renamed::{FromBytes, FromZeros, IntoBytes, TryFromBytes, Unaligned};
+
+use self::util::util::NotZerocopy;
+
+fn main() {}
+
+// Test generic transparent structs
+
+#[derive(IntoBytes, FromBytes, Unaligned)]
+#[zerocopy(crate = "zerocopy_renamed")]
+#[repr(transparent)]
+struct TransparentStruct<T> {
+    inner: T,
+    _phantom: PhantomData<()>,
+}
+
+// It should be legal to derive these traits on a transparent struct, but it
+// must also ensure the traits are only implemented when the inner type
+// implements them.
+util_assert_impl_all!(TransparentStruct<NotZerocopy>: TryFromBytes);
+//~[msrv, stable, nightly]^ ERROR: the trait bound `NotZerocopy: zerocopy_renamed::TryFromBytes` is not satisfied
+
+util_assert_impl_all!(TransparentStruct<NotZerocopy>: FromZeros);
+//~[msrv, stable, nightly]^ ERROR: the trait bound `NotZerocopy: FromZeros` is not satisfied
+
+util_assert_impl_all!(TransparentStruct<NotZerocopy>: FromBytes);
+//~[msrv, stable, nightly]^ ERROR: the trait bound `NotZerocopy: zerocopy_renamed::FromBytes` is not satisfied
+
+util_assert_impl_all!(TransparentStruct<NotZerocopy>: IntoBytes);
+//~[msrv, stable, nightly]^ ERROR: the trait bound `NotZerocopy: zerocopy_renamed::IntoBytes` is not satisfied
+
+util_assert_impl_all!(TransparentStruct<NotZerocopy>: Unaligned);
+//~[msrv, stable, nightly]^ ERROR: the trait bound `NotZerocopy: zerocopy_renamed::Unaligned` is not satisfied