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/enumset/tests/bitset_serde_ops.rs

@@ -0,0 +1,172 @@
+#![cfg(feature = "serde")]
+#![deny(warnings)]
+#![allow(dead_code)]
+
+use enumset::*;
+use serde_derive::*;
+
+// Test resistance against shadowed types.
+type Some = ();
+type None = ();
+type Result = ();
+
+#[derive(Serialize, Deserialize, EnumSetType, Debug)]
+#[enumset(serialize_repr = "list")]
+pub enum ListEnum {
+    A, B, C, D, E, F, G, H,
+}
+
+#[derive(Serialize, Deserialize, EnumSetType, Debug)]
+#[enumset(serialize_repr = "map")]
+pub enum MapEnum {
+    A, B, C, D, E, F, G, H,
+}
+
+#[derive(EnumSetType, Debug)]
+#[enumset(serialize_repr = "array")]
+pub enum ArrayEnum {
+    A, B, C, D, E, F, G, H,
+}
+
+#[derive(EnumSetType, Debug)]
+pub enum LargeEnum {
+    A, B, C, D, E=200, F, G, H,
+}
+
+#[derive(EnumSetType, Debug)]
+#[enumset(serialize_repr = "u128")]
+pub enum ReprEnum {
+    A, B, C, D, E, F, G, H,
+}
+
+#[derive(EnumSetType, Debug)]
+#[enumset(serialize_repr = "u128", serialize_deny_unknown)]
+pub enum DenyUnknownEnum {
+    A, B, C, D, E, F, G, H,
+}
+
+#[derive(EnumSetType, Debug)]
+#[enumset(repr = "u64", serialize_repr = "u32")]
+#[rustfmt::skip]
+pub enum MixedEnum {
+    A = 10, B, C, D, E, F, G, H,
+}
+
+#[derive(EnumSetType, Debug)]
+#[enumset(serialize_repr = "array", serialize_deny_unknown)]
+#[rustfmt::skip]
+pub enum DenyUnknownEnumArray {
+    A = 40, B, C, D, E, F, G, H,
+}
+
+macro_rules! serde_test_simple {
+    ($e:ident, $ser_size:expr) => {
+        const VALUES: &[EnumSet<$e>] = &[
+            enum_set!(),
+            enum_set!($e::A | $e::C | $e::D | $e::F | $e::E | $e::G),
+            enum_set!($e::A),
+            enum_set!($e::H),
+            enum_set!($e::A | $e::B),
+            enum_set!($e::A | $e::B | $e::C | $e::D),
+            enum_set!($e::A | $e::B | $e::C | $e::D | $e::F | $e::G | $e::H),
+            enum_set!($e::G | $e::H),
+            enum_set!($e::E | $e::F | $e::G | $e::H),
+        ];
+
+        #[test]
+        fn serialize_deserialize_test_bincode() {
+            for &value in VALUES {
+                let serialized = bincode::serialize(&value).unwrap();
+                let deserialized = bincode::deserialize::<EnumSet<$e>>(&serialized).unwrap();
+                assert_eq!(value, deserialized);
+                if $ser_size != !0 {
+                    assert_eq!(serialized.len(), $ser_size);
+                }
+            }
+        }
+
+        #[test]
+        fn serialize_deserialize_test_json() {
+            for &value in VALUES {
+                let serialized = serde_json::to_string(&value).unwrap();
+                let deserialized = serde_json::from_str::<EnumSet<$e>>(&serialized).unwrap();
+                assert_eq!(value, deserialized);
+            }
+        }
+    }
+}
+macro_rules! serde_test {
+    ($e:ident, $ser_size:expr) => {
+        serde_test_simple!($e, $ser_size);
+
+        #[test]
+        fn deserialize_all_test() {
+            let serialized = bincode::serialize(&!0u128).unwrap();
+            let deserialized = bincode::deserialize::<EnumSet<$e>>(&serialized).unwrap();
+            assert_eq!(EnumSet::<$e>::all(), deserialized);
+        }
+    }
+}
+macro_rules! tests {
+    ($m:ident, $($tt:tt)*) => { mod $m { use super::*; $($tt)*; } }
+}
+
+#[test]
+fn test_deny_unknown() {
+    let serialized = bincode::serialize(&!0u128).unwrap();
+    let deserialized = bincode::deserialize::<EnumSet<DenyUnknownEnum>>(&serialized);
+    assert!(deserialized.is_err());
+}
+
+#[test]
+fn test_deny_unknown_array() {
+    let serialized = bincode::serialize(&!0u128).unwrap();
+    let deserialized = bincode::deserialize::<EnumSet<DenyUnknownEnumArray>>(&serialized);
+    assert!(deserialized.is_err());
+}
+
+#[test]
+fn test_json_reprs_basic() {
+    assert_eq!(
+        ListEnum::A | ListEnum::C | ListEnum::F,
+        serde_json::from_str::<EnumSet<ListEnum>>(r#"["A","C","F"]"#).unwrap()
+    );
+    assert_eq!(
+        MapEnum::A | MapEnum::C | MapEnum::F,
+        serde_json::from_str::<EnumSet<MapEnum>>(r#"{"A":true,"C":true,"F":true}"#).unwrap()
+    );
+    assert_eq!(
+        ReprEnum::A | ReprEnum::C | ReprEnum::D,
+        serde_json::from_str::<EnumSet<ReprEnum>>("13").unwrap()
+    );
+    assert_eq!(
+        r#"["A","C","F"]"#,
+        serde_json::to_string(&(ListEnum::A | ListEnum::C | ListEnum::F)).unwrap()
+    );
+    assert_eq!(
+        r#"{"A":true,"C":true,"F":true}"#,
+        serde_json::to_string(&(MapEnum::A | MapEnum::C | MapEnum::F)).unwrap()
+    );
+    assert_eq!("13", serde_json::to_string(&(ReprEnum::A | ReprEnum::C | ReprEnum::D)).unwrap());
+    assert_eq!(
+        "[13]",
+        serde_json::to_string(&(ArrayEnum::A | ArrayEnum::C | ArrayEnum::D)).unwrap()
+    );
+}
+
+#[test]
+fn test_json_reprs_edge_cases() {
+    assert_eq!(MapEnum::A | MapEnum::C | MapEnum::F,
+               serde_json::from_str::<EnumSet<MapEnum>>(r#"{"D":false,"A":true,"E":false,"C":true,"F":true}"#).unwrap());
+    assert_eq!(LargeEnum::A | LargeEnum::B | LargeEnum::C | LargeEnum::D,
+               serde_json::from_str::<EnumSet<LargeEnum>>(r#"[15]"#).unwrap());
+}
+
+tests!(list_enum, serde_test_simple!(ListEnum, !0));
+tests!(map_enum, serde_test_simple!(MapEnum, !0));
+tests!(array_enum, serde_test_simple!(ArrayEnum, !0));
+tests!(large_enum, serde_test_simple!(LargeEnum, !0));
+tests!(repr_enum, serde_test!(ReprEnum, 16));
+tests!(deny_unknown_enum, serde_test_simple!(DenyUnknownEnum, 16));
+tests!(mixed_enum, serde_test_simple!(MixedEnum, 4));
+tests!(deny_unknown_enum_array, serde_test_simple!(DenyUnknownEnumArray, 16));