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/thiserror/tests/test_lints.rs

@@ -0,0 +1,109 @@
+#![allow(clippy::mixed_attributes_style)]
+
+use thiserror::Error;
+
+pub use std::error::Error;
+
+#[test]
+fn test_allow_attributes() {
+    #![deny(clippy::allow_attributes)]
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct MyError(#[from] anyhow::Error);
+
+    let _: MyError;
+}
+
+#[test]
+fn test_unused_qualifications() {
+    #![deny(unused_qualifications)]
+
+    // Expansion of derive(Error) macro can't know whether something like
+    // std::error::Error is already imported in the caller's scope so it must
+    // suppress unused_qualifications.
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct MyError;
+
+    let _: MyError;
+}
+
+#[test]
+fn test_needless_lifetimes() {
+    #![allow(dead_code)]
+    #![deny(clippy::elidable_lifetime_names, clippy::needless_lifetimes)]
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub enum MyError<'a> {
+        A(#[from] std::io::Error),
+        B(&'a ()),
+    }
+
+    let _: MyError;
+}
+
+#[test]
+fn test_forbid_needless_lifetimes() {
+    #![forbid(clippy::needless_lifetimes)]
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct MyError(#[from] std::io::Error);
+
+    let _: MyError;
+}
+
+#[test]
+fn test_deprecated() {
+    #![deny(deprecated)]
+
+    #[derive(Error, Debug)]
+    #[deprecated]
+    #[error("...")]
+    pub struct DeprecatedStruct;
+
+    #[derive(Error, Debug)]
+    #[error("{message} {}", .message)]
+    pub struct DeprecatedStructField {
+        #[deprecated]
+        message: String,
+    }
+
+    #[derive(Error, Debug)]
+    #[deprecated]
+    pub enum DeprecatedEnum {
+        #[error("...")]
+        Variant,
+    }
+
+    #[derive(Error, Debug)]
+    pub enum DeprecatedVariant {
+        #[deprecated]
+        #[error("...")]
+        Variant,
+    }
+
+    #[derive(Error, Debug)]
+    pub enum DeprecatedFrom {
+        #[error(transparent)]
+        Variant(
+            #[from]
+            #[allow(deprecated)]
+            DeprecatedStruct,
+        ),
+    }
+
+    #[allow(deprecated)]
+    let _: DeprecatedStruct;
+    #[allow(deprecated)]
+    let _: DeprecatedStructField;
+    #[allow(deprecated)]
+    let _ = DeprecatedEnum::Variant;
+    #[allow(deprecated)]
+    let _ = DeprecatedVariant::Variant;
+    #[allow(deprecated)]
+    let _ = DeprecatedFrom::Variant(DeprecatedStruct);
+}