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/struct_to_bytes.rs

@@ -0,0 +1,229 @@
+// 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.
+
+// See comment in `include.rs` for why we disable the prelude.
+#![no_implicit_prelude]
+#![allow(warnings)]
+
+include!("include.rs");
+
+// A struct is `IntoBytes` if:
+// - all fields are `IntoBytes`
+// - `repr(C)` or `repr(transparent)` and
+//   - no padding (size of struct equals sum of size of field types)
+// - `repr(packed)`
+
+#[derive(imp::IntoBytes)]
+#[zerocopy(crate = "zerocopy_renamed")]
+#[repr(C)]
+struct CZst;
+
+util_assert_impl_all!(CZst: imp::IntoBytes);
+
+#[derive(imp::IntoBytes)]
+#[zerocopy(crate = "zerocopy_renamed")]
+#[repr(C)]
+struct C {
+    a: u8,
+    b: u8,
+    c: util::AU16,
+}
+
+util_assert_impl_all!(C: imp::IntoBytes);
+
+#[derive(imp::IntoBytes)]
+#[zerocopy(crate = "zerocopy_renamed")]
+#[repr(C)]
+struct SyntacticUnsized {
+    a: u8,
+    b: u8,
+    c: [util::AU16],
+}
+
+util_assert_impl_all!(C: imp::IntoBytes);
+
+#[derive(imp::IntoBytes)]
+#[zerocopy(crate = "zerocopy_renamed")]
+#[repr(transparent)]
+struct Transparent {
+    a: u8,
+    b: (),
+}
+
+util_assert_impl_all!(Transparent: imp::IntoBytes);
+
+#[derive(imp::IntoBytes)]
+#[zerocopy(crate = "zerocopy_renamed")]
+#[repr(transparent)]
+struct TransparentGeneric<T: ?imp::Sized> {
+    a: (),
+    b: T,
+}
+
+util_assert_impl_all!(TransparentGeneric<u64>: imp::IntoBytes);
+util_assert_impl_all!(TransparentGeneric<[u64]>: imp::IntoBytes);
+
+#[derive(imp::IntoBytes)]
+#[zerocopy(crate = "zerocopy_renamed")]
+#[repr(C, packed)]
+struct CZstPacked;
+
+util_assert_impl_all!(CZstPacked: imp::IntoBytes);
+
+#[derive(imp::IntoBytes)]
+#[zerocopy(crate = "zerocopy_renamed")]
+#[repr(C, packed)]
+struct CPacked {
+    a: u8,
+    // NOTE: The `u16` type is not guaranteed to have alignment 2, although it
+    // does on many platforms. However, to fix this would require a custom type
+    // with a `#[repr(align(2))]` attribute, and `#[repr(packed)]` types are not
+    // allowed to transitively contain `#[repr(align(...))]` types. Thus, we
+    // have no choice but to use `u16` here. Luckily, these tests run in CI on
+    // platforms on which `u16` has alignment 2, so this isn't that big of a
+    // deal.
+    b: u16,
+}
+
+util_assert_impl_all!(CPacked: imp::IntoBytes);
+
+#[derive(imp::IntoBytes)]
+#[zerocopy(crate = "zerocopy_renamed")]
+#[repr(C, packed(2))]
+// The same caveats as for CPacked apply - we're assuming u64 is at least
+// 4-byte aligned by default. Without packed(2), this should fail, as there
+// would be padding between a/b assuming u64 is 4+ byte aligned.
+struct CPacked2 {
+    a: u16,
+    b: u64,
+}
+
+util_assert_impl_all!(CPacked2: imp::IntoBytes);
+
+#[derive(imp::IntoBytes)]
+#[zerocopy(crate = "zerocopy_renamed")]
+#[repr(C, packed)]
+struct CPackedGeneric<T, U: ?imp::Sized> {
+    t: T,
+    // Unsized types stored in `repr(packed)` structs must not be dropped
+    // because dropping them in-place might be unsound depending on the
+    // alignment of the outer struct. Sized types can be dropped by first being
+    // moved to an aligned stack variable, but this isn't possible with unsized
+    // types.
+    u: imp::ManuallyDrop<U>,
+}
+
+util_assert_impl_all!(CPackedGeneric<u8, util::AU16>: imp::IntoBytes);
+util_assert_impl_all!(CPackedGeneric<u8, [util::AU16]>: imp::IntoBytes);
+
+#[derive(imp::IntoBytes)]
+#[zerocopy(crate = "zerocopy_renamed")]
+#[repr(packed)]
+struct PackedGeneric<T, U: ?imp::Sized> {
+    t: T,
+    // Unsized types stored in `repr(packed)` structs must not be dropped
+    // because dropping them in-place might be unsound depending on the
+    // alignment of the outer struct. Sized types can be dropped by first being
+    // moved to an aligned stack variable, but this isn't possible with unsized
+    // types.
+    u: imp::ManuallyDrop<U>,
+}
+
+util_assert_impl_all!(PackedGeneric<u8, util::AU16>: imp::IntoBytes);
+util_assert_impl_all!(PackedGeneric<u8, [util::AU16]>: imp::IntoBytes);
+
+// This test is non-portable, but works so long as Rust happens to lay this
+// struct out with no padding.
+#[derive(imp::IntoBytes)]
+#[zerocopy(crate = "zerocopy_renamed")]
+struct Unpacked {
+    a: u8,
+    b: u8,
+}
+
+util_assert_impl_all!(Unpacked: imp::IntoBytes);
+
+#[derive(imp::IntoBytes)]
+#[zerocopy(crate = "zerocopy_renamed")]
+#[repr(C)]
+struct ReprCGenericOneField<T: ?imp::Sized> {
+    t: T,
+}
+
+// Even though `ReprCGenericOneField` has generic type arguments, since it only
+// has one field, we don't require that its field types implement `Unaligned`.
+util_assert_impl_all!(ReprCGenericOneField<util::AU16>: imp::IntoBytes);
+util_assert_impl_all!(ReprCGenericOneField<[util::AU16]>: imp::IntoBytes);
+
+#[derive(imp::IntoBytes)]
+#[zerocopy(crate = "zerocopy_renamed")]
+#[repr(C)]
+struct ReprCGenericMultipleFields<T, U: ?imp::Sized> {
+    t: T,
+    u: U,
+}
+
+// Since `ReprCGenericMultipleFields` is generic and has more than one field,
+// all field types must implement `Unaligned`.
+util_assert_impl_all!(ReprCGenericMultipleFields<u8, [u8; 2]>: imp::IntoBytes);
+util_assert_impl_all!(ReprCGenericMultipleFields<u8, [[u8; 2]]>: imp::IntoBytes);
+util_assert_not_impl_any!(ReprCGenericMultipleFields<u8, util::AU16>: imp::IntoBytes);
+util_assert_not_impl_any!(ReprCGenericMultipleFields<u8, [util::AU16]>: imp::IntoBytes);
+
+#[derive(imp::IntoBytes)]
+#[zerocopy(crate = "zerocopy_renamed")]
+#[repr(transparent)]
+struct Unsized {
+    a: [u8],
+}
+
+util_assert_impl_all!(Unsized: imp::IntoBytes);
+
+#[derive(imp::IntoBytes)]
+#[zerocopy(crate = "zerocopy_renamed")]
+#[repr(C, align(2))]
+struct UnsizedAligned {
+    a: [[u8; 2]],
+}
+
+util_assert_impl_all!(UnsizedAligned: imp::IntoBytes);
+
+// Deriving `IntoBytes` should work if the struct has bounded parameters.
+
+#[derive(imp::IntoBytes)]
+#[zerocopy(crate = "zerocopy_renamed")]
+#[repr(transparent)]
+struct WithParams<'a: 'b, 'b: 'a, T: 'a + 'b + imp::IntoBytes, const N: usize>(
+    [T; N],
+    imp::PhantomData<&'a &'b ()>,
+)
+where
+    'a: 'b,
+    'b: 'a,
+    T: 'a + 'b + imp::IntoBytes;
+
+util_assert_impl_all!(WithParams<'static, 'static, u8, 42>: imp::IntoBytes);
+
+// Test for the failure reported in #1182.
+
+#[derive(imp::IntoBytes)]
+#[zerocopy(crate = "zerocopy_renamed")]
+#[repr(C, packed)]
+pub struct IndexEntryFlags(u8);
+
+#[derive(imp::IntoBytes)]
+#[zerocopy(crate = "zerocopy_renamed")]
+#[repr(C, packed)]
+pub struct IndexEntry<const SIZE_BLOCK_ID: usize> {
+    block_number: imp::native_endian::U64,
+    flags: IndexEntryFlags,
+    block_id: [u8; SIZE_BLOCK_ID],
+}
+
+util_assert_impl_all!(IndexEntry<0>: imp::IntoBytes);
+util_assert_impl_all!(IndexEntry<1>: imp::IntoBytes);