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/enum-as-inner/tests/unnamed.rs

@@ -0,0 +1,100 @@
+#![warn(
+    clippy::default_trait_access,
+    clippy::dbg_macro,
+    clippy::print_stdout,
+    clippy::unimplemented,
+    clippy::use_self,
+    missing_copy_implementations,
+    missing_docs,
+    non_snake_case,
+    non_upper_case_globals,
+    rust_2018_idioms,
+    unreachable_pub
+)]
+
+use enum_as_inner::EnumAsInner;
+
+pub mod name_collisions {
+    #![allow(dead_code, missing_copy_implementations, missing_docs)]
+    pub struct Option;
+    pub struct Some;
+    pub struct None;
+    pub struct Result;
+    pub struct Ok;
+    pub struct Err;
+}
+#[allow(unused_imports)]
+use name_collisions::*;
+
+#[derive(Debug, EnumAsInner)]
+enum ManyVariants {
+    One(u32),
+    Two(u32, i32),
+    Three(bool, u32, i64),
+}
+
+#[test]
+fn test_one_unnamed() {
+    let mut many = ManyVariants::One(1);
+
+    assert!(many.is_one());
+    assert!(!many.is_two());
+    assert!(!many.is_three());
+
+    assert!(many.as_one().is_some());
+    assert!(many.as_two().is_none());
+    assert!(many.as_three().is_none());
+
+    assert!(many.as_one_mut().is_some());
+    assert!(many.as_two_mut().is_none());
+    assert!(many.as_three_mut().is_none());
+
+    assert_eq!(*many.as_one().unwrap(), 1_u32);
+    assert_eq!(*many.as_one_mut().unwrap(), 1_u32);
+    assert_eq!(many.into_one().unwrap(), 1_u32);
+}
+
+#[test]
+fn test_two_unnamed() {
+    let mut many = ManyVariants::Two(1, 2);
+
+    assert!(!many.is_one());
+    assert!(many.is_two());
+    assert!(!many.is_three());
+
+    assert!(many.as_one().is_none());
+    assert!(many.as_two().is_some());
+    assert!(many.as_three().is_none());
+
+    assert!(many.as_one_mut().is_none());
+    assert!(many.as_two_mut().is_some());
+    assert!(many.as_three_mut().is_none());
+
+    assert_eq!(many.as_two().unwrap(), (&1_u32, &2_i32));
+    assert_eq!(many.as_two_mut().unwrap(), (&mut 1_u32, &mut 2_i32));
+    assert_eq!(many.into_two().unwrap(), (1_u32, 2_i32));
+}
+
+#[test]
+fn test_three_unnamed() {
+    let mut many = ManyVariants::Three(true, 1, 2);
+
+    assert!(!many.is_one());
+    assert!(!many.is_two());
+    assert!(many.is_three());
+
+    assert!(many.as_one().is_none());
+    assert!(many.as_two().is_none());
+    assert!(many.as_three().is_some());
+
+    assert!(many.as_one_mut().is_none());
+    assert!(many.as_two_mut().is_none());
+    assert!(many.as_three_mut().is_some());
+
+    assert_eq!(many.as_three().unwrap(), (&true, &1_u32, &2_i64));
+    assert_eq!(
+        many.as_three_mut().unwrap(),
+        (&mut true, &mut 1_u32, &mut 2_i64)
+    );
+    assert_eq!(many.into_three().unwrap(), (true, 1_u32, 2_i64));
+}