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/deprecated.rs

@@ -0,0 +1,131 @@
+// Copyright 2024 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.
+
+// See comment in `include.rs` for why we disable the prelude.
+#![no_implicit_prelude]
+#![allow(warnings)]
+#![deny(deprecated)]
+
+include!("include.rs");
+
+// Make sure no deprecation warnings are generated from our derives (see #553).
+
+#[macro_export]
+macro_rules! test {
+    ($name:ident => $ty:item => $($trait:ident),*) => {
+        #[allow(non_snake_case)]
+        mod $name {
+            $(
+                mod $trait {
+                    use super::super::*;
+
+                    #[deprecated = "do not use"]
+                    #[derive(imp::$trait)]
+                    #[zerocopy(crate = "zerocopy_renamed")]
+                    $ty
+
+                    #[allow(deprecated)]
+                    fn _allow_deprecated() {
+                        util_assert_impl_all!($name: imp::$trait);
+                    }
+                }
+            )*
+        }
+    };
+}
+
+// NOTE: `FromBytes` is tested separately in `enum_from_bytes.rs` since it
+// requires 256-variant enums which are extremely verbose; such enums are
+// already in that file.
+test!(Enum => #[repr(u8)] enum Enum { A, } => TryFromBytes, FromZeros, KnownLayout, Immutable, IntoBytes, Unaligned);
+
+test!(Struct => #[repr(C)] struct Struct; => TryFromBytes, FromZeros, FromBytes, KnownLayout, Immutable, IntoBytes, Unaligned);
+
+test!(Union => #[repr(C)] union Union{ a: (), } => TryFromBytes, FromZeros, FromBytes, KnownLayout, Immutable, IntoBytes, Unaligned);
+
+// Tests for ByteHash and ByteEq which require IntoBytes + Immutable
+mod enum_hash_eq {
+    mod ByteHash {
+        use super::super::*;
+        #[deprecated = "do not use"]
+        #[derive(imp::ByteHash, imp::IntoBytes, imp::Immutable)]
+        #[zerocopy(crate = "zerocopy_renamed")]
+        #[repr(u8)]
+        enum Enum {
+            A,
+        }
+
+        #[allow(deprecated)]
+        fn _allow_deprecated() {
+            util_assert_impl_all!(Enum: ::core::hash::Hash);
+        }
+    }
+    mod ByteEq {
+        use super::super::*;
+        #[deprecated = "do not use"]
+        #[derive(imp::ByteEq, imp::IntoBytes, imp::Immutable)]
+        #[zerocopy(crate = "zerocopy_renamed")]
+        #[repr(u8)]
+        enum Enum {
+            A,
+        }
+
+        #[allow(deprecated)]
+        fn _allow_deprecated() {
+            util_assert_impl_all!(Enum: ::core::cmp::PartialEq, ::core::cmp::Eq);
+        }
+    }
+}
+
+mod struct_hash_eq {
+    mod ByteHash {
+        use super::super::*;
+        #[deprecated = "do not use"]
+        #[derive(imp::ByteHash, imp::IntoBytes, imp::Immutable)]
+        #[zerocopy(crate = "zerocopy_renamed")]
+        #[repr(C)]
+        struct Struct;
+
+        #[allow(deprecated)]
+        fn _allow_deprecated() {
+            util_assert_impl_all!(Struct: ::core::hash::Hash);
+        }
+    }
+    mod ByteEq {
+        use super::super::*;
+        #[deprecated = "do not use"]
+        #[derive(imp::ByteEq, imp::IntoBytes, imp::Immutable)]
+        #[zerocopy(crate = "zerocopy_renamed")]
+        #[repr(C)]
+        struct Struct;
+
+        #[allow(deprecated)]
+        fn _allow_deprecated() {
+            util_assert_impl_all!(Struct: ::core::cmp::PartialEq, ::core::cmp::Eq);
+        }
+    }
+}
+
+// Tests for SplitAt which requires repr(C) and at least one field
+mod split_at_test {
+    mod SplitAt {
+        use super::super::*;
+        #[deprecated = "do not use"]
+        #[derive(imp::SplitAt, imp::KnownLayout)]
+        #[zerocopy(crate = "zerocopy_renamed")]
+        #[repr(C)]
+        struct Struct {
+            a: [u8],
+        }
+
+        #[allow(deprecated)]
+        fn _allow_deprecated() {
+            util_assert_impl_all!(Struct: imp::SplitAt);
+        }
+    }
+}