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/darling/tests/from_generics.rs

@@ -0,0 +1,175 @@
+//! Tests for `FromGenerics`, and - indirectly - `FromGenericParam`.
+//! These tests assume `FromTypeParam` is working and only look at whether the wrappers for magic
+//! fields are working as expected.
+
+use darling::{
+    ast::{self, GenericParamExt},
+    util::{Ignored, WithOriginal},
+    FromDeriveInput, FromTypeParam, Result,
+};
+
+#[derive(FromDeriveInput)]
+#[darling(attributes(lorem))]
+struct MyReceiver {
+    pub generics: ast::Generics<ast::GenericParam<MyTypeParam>>,
+}
+
+#[derive(FromTypeParam)]
+#[darling(attributes(lorem))]
+struct MyTypeParam {
+    pub ident: syn::Ident,
+    #[darling(default)]
+    pub foo: bool,
+    pub bar: Option<String>,
+}
+
+fn fdi<T: FromDeriveInput>(src: &str) -> Result<T> {
+    FromDeriveInput::from_derive_input(&syn::parse_str(src).expect("Source parses"))
+}
+
+/// Verify that `ast::Generics` is populated correctly when there is no generics declaration
+#[test]
+fn no_generics() {
+    let rec: MyReceiver = fdi("struct Baz;").expect("Input is well-formed");
+    assert!(rec.generics.where_clause.is_none());
+    assert_eq!(rec.generics.params.len(), 0);
+}
+
+#[test]
+#[allow(clippy::bool_assert_comparison)]
+fn expand_some() {
+    let rec: MyReceiver = fdi(r#"
+        struct Baz<
+            'a,
+            #[lorem(foo)] T,
+            #[lorem(bar = "x")] U: Eq + ?Sized
+        >(&'a T, U);
+    "#)
+    .expect("Input is well-formed");
+    assert!(rec.generics.where_clause.is_none());
+
+    // Make sure we've preserved the lifetime param, though we don't do anything with it.
+    assert!(rec.generics.params[0].as_lifetime_param().is_some());
+
+    let mut ty_param_iter = rec.generics.type_params();
+
+    let first = ty_param_iter
+        .next()
+        .expect("type_params should not be empty");
+    assert!(first.bar.is_none());
+    assert!(first.foo);
+    assert_eq!(first.ident, "T");
+
+    let second = ty_param_iter
+        .next()
+        .expect("type_params should have a second value");
+    assert_eq!(
+        second
+            .bar
+            .as_ref()
+            .expect("Second type param should set bar"),
+        "x"
+    );
+    assert_eq!(second.foo, false);
+    assert_eq!(second.ident, "U");
+}
+
+/// Verify ≤0.4.1 behavior - where `generics` had to be `syn::Generics` - keeps working.
+#[test]
+fn passthrough() {
+    #[derive(FromDeriveInput)]
+    struct PassthroughReceiver {
+        pub generics: syn::Generics,
+    }
+
+    let rec: PassthroughReceiver = fdi(r#"
+        struct Baz<
+            'a,
+            #[lorem(foo)] T,
+            #[lorem(bar = "x")] U: Eq + ?Sized
+        >(&'a T, U);
+    "#)
+    .expect("Input is well-formed");
+
+    let mut type_param_iter = rec.generics.type_params();
+    assert!(type_param_iter.next().is_some());
+}
+
+/// Verify that `where_clause` is passed through when it exists.
+/// As of 0.4.1, there is no `FromWhereClause` trait, so other types aren't supported
+/// for that field.
+#[test]
+fn where_clause() {
+    let rec: MyReceiver = fdi(r#"
+        struct Baz<
+            'a,
+            #[lorem(foo)] T,
+            #[lorem(bar = "x")] U: Eq + ?Sized
+        >(&'a T, U) where T: Into<String>;
+    "#)
+    .expect("Input is well-formed");
+
+    assert!(rec.generics.where_clause.is_some());
+}
+
+/// Test that `WithOriginal` works for generics.
+#[test]
+fn with_original() {
+    #[derive(FromDeriveInput)]
+    struct WorigReceiver {
+        generics: WithOriginal<ast::Generics<ast::GenericParam<MyTypeParam>>, syn::Generics>,
+    }
+
+    let rec: WorigReceiver = fdi(r#"
+        struct Baz<
+            'a,
+            #[lorem(foo)] T,
+            #[lorem(bar = "x")] U: Eq + ?Sized
+        >(&'a T, U) where T: Into<String>;
+    "#)
+    .expect("Input is well-formed");
+
+    // Make sure we haven't lost anything in the conversion
+    assert_eq!(rec.generics.parsed.params.len(), 3);
+    assert_eq!(rec.generics.original.params.len(), 3);
+
+    let parsed_t: &MyTypeParam = rec.generics.parsed.params[1]
+        .as_type_param()
+        .expect("Second argument should be type param");
+
+    // Make sure the first type param in each case is T
+    assert_eq!(parsed_t.ident, "T");
+    assert_eq!(
+        rec.generics
+            .original
+            .type_params()
+            .next()
+            .expect("First type param should exist")
+            .ident,
+        "T"
+    );
+
+    // Make sure we actually parsed the first type param
+    assert!(parsed_t.foo);
+    assert!(parsed_t.bar.is_none());
+}
+
+/// Make sure generics can be ignored
+#[test]
+fn ignored() {
+    #[derive(FromDeriveInput)]
+    struct IgnoredReceiver {
+        generics: Ignored,
+    }
+
+    let rec: IgnoredReceiver = fdi(r#"
+        struct Baz<
+            'a,
+            #[lorem(foo)] T,
+            #[lorem(bar = "x")] U: Eq + ?Sized
+        >(&'a T, U) where T: Into<String>;
+    "#)
+    .expect("Input is well-formed");
+
+    assert_eq!(Ignored, rec.generics);
+}