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/rustversion/tests/test_parse.rs

@@ -0,0 +1,103 @@
+#![allow(
+    clippy::derive_partial_eq_without_eq,
+    clippy::enum_glob_use,
+    clippy::must_use_candidate
+)]
+
+include!("../build/rustc.rs");
+
+#[test]
+fn test_parse() {
+    let cases = &[
+        (
+            "rustc 1.0.0 (a59de37e9 2015-05-13) (built 2015-05-14)",
+            Version {
+                minor: 0,
+                patch: 0,
+                channel: Stable,
+            },
+        ),
+        (
+            "rustc 1.18.0",
+            Version {
+                minor: 18,
+                patch: 0,
+                channel: Stable,
+            },
+        ),
+        (
+            "rustc 1.24.1 (d3ae9a9e0 2018-02-27)",
+            Version {
+                minor: 24,
+                patch: 1,
+                channel: Stable,
+            },
+        ),
+        (
+            "rustc 1.35.0-beta.3 (c13114dc8 2019-04-27)",
+            Version {
+                minor: 35,
+                patch: 0,
+                channel: Beta,
+            },
+        ),
+        (
+            "rustc 1.36.0-nightly (938d4ffe1 2019-04-27)",
+            Version {
+                minor: 36,
+                patch: 0,
+                channel: Nightly(Date {
+                    year: 2019,
+                    month: 4,
+                    day: 27,
+                }),
+            },
+        ),
+        (
+            "rustc 1.36.0-dev",
+            Version {
+                minor: 36,
+                patch: 0,
+                channel: Dev,
+            },
+        ),
+        (
+            "rustc 1.36.0-nightly",
+            Version {
+                minor: 36,
+                patch: 0,
+                channel: Dev,
+            },
+        ),
+        (
+            "warning: invalid logging spec 'warning', ignoring it
+             rustc 1.30.0-nightly (3bc2ca7e4 2018-09-20)",
+            Version {
+                minor: 30,
+                patch: 0,
+                channel: Nightly(Date {
+                    year: 2018,
+                    month: 9,
+                    day: 20,
+                }),
+            },
+        ),
+        (
+            "rustc 1.52.1-nightly (gentoo)",
+            Version {
+                minor: 52,
+                patch: 1,
+                channel: Dev,
+            },
+        ),
+    ];
+
+    for (string, expected) in cases {
+        match parse(string) {
+            ParseResult::Success(version) => assert_eq!(version, *expected),
+            ParseResult::OopsClippy | ParseResult::OopsMirai | ParseResult::Unrecognized => {
+                panic!("unrecognized: {:?}", string);
+            }
+        }
+    }
+}