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/issue_2880.rs

@@ -0,0 +1,292 @@
+// Copyright 2026 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.
+
+#![no_implicit_prelude]
+#![deny(non_ascii_idents)]
+#![allow(dead_code)]
+
+include!("include.rs");
+
+// FIXME(#2880): Derive `FromBytes` in all types once we support non-ASCII
+// idents.
+
+#[derive(imp::KnownLayout, imp::IntoBytes, imp::Immutable)]
+#[zerocopy(crate = "zerocopy_renamed")]
+#[repr(C)]
+struct TestStruct {
+    a: u8,
+}
+
+#[derive(imp::KnownLayout, imp::IntoBytes, imp::Immutable)]
+#[zerocopy(crate = "zerocopy_renamed")]
+#[repr(C)]
+union TestUnion {
+    a: u8,
+}
+
+#[derive(imp::KnownLayout, imp::FromBytes, imp::IntoBytes, imp::Immutable)]
+#[zerocopy(crate = "zerocopy_renamed")]
+#[repr(u8)]
+enum FooU8 {
+    Variant0,
+    Variant1,
+    Variant2,
+    Variant3,
+    Variant4,
+    Variant5,
+    Variant6,
+    Variant7,
+    Variant8,
+    Variant9,
+    Variant10,
+    Variant11,
+    Variant12,
+    Variant13,
+    Variant14,
+    Variant15,
+    Variant16,
+    Variant17,
+    Variant18,
+    Variant19,
+    Variant20,
+    Variant21,
+    Variant22,
+    Variant23,
+    Variant24,
+    Variant25,
+    Variant26,
+    Variant27,
+    Variant28,
+    Variant29,
+    Variant30,
+    Variant31,
+    Variant32,
+    Variant33,
+    Variant34,
+    Variant35,
+    Variant36,
+    Variant37,
+    Variant38,
+    Variant39,
+    Variant40,
+    Variant41,
+    Variant42,
+    Variant43,
+    Variant44,
+    Variant45,
+    Variant46,
+    Variant47,
+    Variant48,
+    Variant49,
+    Variant50,
+    Variant51,
+    Variant52,
+    Variant53,
+    Variant54,
+    Variant55,
+    Variant56,
+    Variant57,
+    Variant58,
+    Variant59,
+    Variant60,
+    Variant61,
+    Variant62,
+    Variant63,
+    Variant64,
+    Variant65,
+    Variant66,
+    Variant67,
+    Variant68,
+    Variant69,
+    Variant70,
+    Variant71,
+    Variant72,
+    Variant73,
+    Variant74,
+    Variant75,
+    Variant76,
+    Variant77,
+    Variant78,
+    Variant79,
+    Variant80,
+    Variant81,
+    Variant82,
+    Variant83,
+    Variant84,
+    Variant85,
+    Variant86,
+    Variant87,
+    Variant88,
+    Variant89,
+    Variant90,
+    Variant91,
+    Variant92,
+    Variant93,
+    Variant94,
+    Variant95,
+    Variant96,
+    Variant97,
+    Variant98,
+    Variant99,
+    Variant100,
+    Variant101,
+    Variant102,
+    Variant103,
+    Variant104,
+    Variant105,
+    Variant106,
+    Variant107,
+    Variant108,
+    Variant109,
+    Variant110,
+    Variant111,
+    Variant112,
+    Variant113,
+    Variant114,
+    Variant115,
+    Variant116,
+    Variant117,
+    Variant118,
+    Variant119,
+    Variant120,
+    Variant121,
+    Variant122,
+    Variant123,
+    Variant124,
+    Variant125,
+    Variant126,
+    Variant127,
+    Variant128,
+    Variant129,
+    Variant130,
+    Variant131,
+    Variant132,
+    Variant133,
+    Variant134,
+    Variant135,
+    Variant136,
+    Variant137,
+    Variant138,
+    Variant139,
+    Variant140,
+    Variant141,
+    Variant142,
+    Variant143,
+    Variant144,
+    Variant145,
+    Variant146,
+    Variant147,
+    Variant148,
+    Variant149,
+    Variant150,
+    Variant151,
+    Variant152,
+    Variant153,
+    Variant154,
+    Variant155,
+    Variant156,
+    Variant157,
+    Variant158,
+    Variant159,
+    Variant160,
+    Variant161,
+    Variant162,
+    Variant163,
+    Variant164,
+    Variant165,
+    Variant166,
+    Variant167,
+    Variant168,
+    Variant169,
+    Variant170,
+    Variant171,
+    Variant172,
+    Variant173,
+    Variant174,
+    Variant175,
+    Variant176,
+    Variant177,
+    Variant178,
+    Variant179,
+    Variant180,
+    Variant181,
+    Variant182,
+    Variant183,
+    Variant184,
+    Variant185,
+    Variant186,
+    Variant187,
+    Variant188,
+    Variant189,
+    Variant190,
+    Variant191,
+    Variant192,
+    Variant193,
+    Variant194,
+    Variant195,
+    Variant196,
+    Variant197,
+    Variant198,
+    Variant199,
+    Variant200,
+    Variant201,
+    Variant202,
+    Variant203,
+    Variant204,
+    Variant205,
+    Variant206,
+    Variant207,
+    Variant208,
+    Variant209,
+    Variant210,
+    Variant211,
+    Variant212,
+    Variant213,
+    Variant214,
+    Variant215,
+    Variant216,
+    Variant217,
+    Variant218,
+    Variant219,
+    Variant220,
+    Variant221,
+    Variant222,
+    Variant223,
+    Variant224,
+    Variant225,
+    Variant226,
+    Variant227,
+    Variant228,
+    Variant229,
+    Variant230,
+    Variant231,
+    Variant232,
+    Variant233,
+    Variant234,
+    Variant235,
+    Variant236,
+    Variant237,
+    Variant238,
+    Variant239,
+    Variant240,
+    Variant241,
+    Variant242,
+    Variant243,
+    Variant244,
+    Variant245,
+    Variant246,
+    Variant247,
+    Variant248,
+    Variant249,
+    Variant250,
+    Variant251,
+    Variant252,
+    Variant253,
+    Variant254,
+    Variant255,
+}