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_backtrace.rs

@@ -0,0 +1,289 @@
+#![cfg(feature = "std")]
+#![cfg_attr(thiserror_nightly_testing, feature(error_generic_member_access))]
+
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error("...")]
+pub struct Inner;
+
+#[cfg(thiserror_nightly_testing)]
+#[derive(Error, Debug)]
+#[error("...")]
+pub struct InnerBacktrace {
+    backtrace: std::backtrace::Backtrace,
+}
+
+#[cfg(thiserror_nightly_testing)]
+pub mod structs {
+    use super::{Inner, InnerBacktrace};
+    use std::backtrace::Backtrace;
+    use std::error::{self, Error};
+    use std::sync::Arc;
+    use thiserror::Error;
+
+    mod not_backtrace {
+        #[derive(Debug)]
+        pub struct Backtrace;
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct PlainBacktrace {
+        backtrace: Backtrace,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct ExplicitBacktrace {
+        #[backtrace]
+        backtrace: Backtrace,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct NotBacktrace {
+        backtrace: crate::structs::not_backtrace::r#Backtrace,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct OptBacktrace {
+        #[backtrace]
+        backtrace: Option<Backtrace>,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct ArcBacktrace {
+        #[backtrace]
+        backtrace: Arc<Backtrace>,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct BacktraceFrom {
+        #[from]
+        source: Inner,
+        #[backtrace]
+        backtrace: Backtrace,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct CombinedBacktraceFrom {
+        #[from]
+        #[backtrace]
+        source: InnerBacktrace,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct OptBacktraceFrom {
+        #[from]
+        source: Inner,
+        #[backtrace]
+        backtrace: Option<Backtrace>,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct ArcBacktraceFrom {
+        #[from]
+        source: Inner,
+        #[backtrace]
+        backtrace: Arc<Backtrace>,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct AnyhowBacktrace {
+        #[backtrace]
+        source: anyhow::Error,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct BoxDynErrorBacktrace {
+        #[backtrace]
+        source: Box<dyn Error>,
+    }
+
+    #[test]
+    fn test_backtrace() {
+        let error = PlainBacktrace {
+            backtrace: Backtrace::capture(),
+        };
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = ExplicitBacktrace {
+            backtrace: Backtrace::capture(),
+        };
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = OptBacktrace {
+            backtrace: Some(Backtrace::capture()),
+        };
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = ArcBacktrace {
+            backtrace: Arc::new(Backtrace::capture()),
+        };
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = BacktraceFrom::from(Inner);
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = CombinedBacktraceFrom::from(InnerBacktrace {
+            backtrace: Backtrace::capture(),
+        });
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = OptBacktraceFrom::from(Inner);
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = ArcBacktraceFrom::from(Inner);
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = AnyhowBacktrace {
+            source: anyhow::Error::msg("..."),
+        };
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = BoxDynErrorBacktrace {
+            source: Box::new(PlainBacktrace {
+                backtrace: Backtrace::capture(),
+            }),
+        };
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+    }
+}
+
+#[cfg(thiserror_nightly_testing)]
+pub mod enums {
+    use super::{Inner, InnerBacktrace};
+    use std::backtrace::Backtrace;
+    use std::error;
+    use std::sync::Arc;
+    use thiserror::Error;
+
+    #[derive(Error, Debug)]
+    pub enum PlainBacktrace {
+        #[error("...")]
+        Test { backtrace: Backtrace },
+    }
+
+    #[derive(Error, Debug)]
+    pub enum ExplicitBacktrace {
+        #[error("...")]
+        Test {
+            #[backtrace]
+            backtrace: Backtrace,
+        },
+    }
+
+    #[derive(Error, Debug)]
+    pub enum OptBacktrace {
+        #[error("...")]
+        Test {
+            #[backtrace]
+            backtrace: Option<Backtrace>,
+        },
+    }
+
+    #[derive(Error, Debug)]
+    pub enum ArcBacktrace {
+        #[error("...")]
+        Test {
+            #[backtrace]
+            backtrace: Arc<Backtrace>,
+        },
+    }
+
+    #[derive(Error, Debug)]
+    pub enum BacktraceFrom {
+        #[error("...")]
+        Test {
+            #[from]
+            source: Inner,
+            #[backtrace]
+            backtrace: Backtrace,
+        },
+    }
+
+    #[derive(Error, Debug)]
+    pub enum CombinedBacktraceFrom {
+        #[error("...")]
+        Test {
+            #[from]
+            #[backtrace]
+            source: InnerBacktrace,
+        },
+    }
+
+    #[derive(Error, Debug)]
+    pub enum OptBacktraceFrom {
+        #[error("...")]
+        Test {
+            #[from]
+            source: Inner,
+            #[backtrace]
+            backtrace: Option<Backtrace>,
+        },
+    }
+
+    #[derive(Error, Debug)]
+    pub enum ArcBacktraceFrom {
+        #[error("...")]
+        Test {
+            #[from]
+            source: Inner,
+            #[backtrace]
+            backtrace: Arc<Backtrace>,
+        },
+    }
+
+    #[test]
+    fn test_backtrace() {
+        let error = PlainBacktrace::Test {
+            backtrace: Backtrace::capture(),
+        };
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = ExplicitBacktrace::Test {
+            backtrace: Backtrace::capture(),
+        };
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = OptBacktrace::Test {
+            backtrace: Some(Backtrace::capture()),
+        };
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = ArcBacktrace::Test {
+            backtrace: Arc::new(Backtrace::capture()),
+        };
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = BacktraceFrom::from(Inner);
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = CombinedBacktraceFrom::from(InnerBacktrace {
+            backtrace: Backtrace::capture(),
+        });
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = OptBacktraceFrom::from(Inner);
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = ArcBacktraceFrom::from(Inner);
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+    }
+}
+
+#[test]
+#[cfg_attr(
+    not(thiserror_nightly_testing),
+    ignore = "requires `--cfg=thiserror_nightly_testing`"
+)]
+fn test_backtrace() {}