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/winnow/examples/arithmetic/bench.rs

@@ -0,0 +1,33 @@
+mod parser;
+mod parser_ast;
+mod parser_lexer;
+
+use winnow::prelude::*;
+
+#[allow(clippy::eq_op, clippy::erasing_op)]
+fn arithmetic(c: &mut criterion::Criterion) {
+    let data = "  2*2 / ( 5 - 1) + 3 / 4 * (2 - 7 + 567 *12 /2) + 3*(1+2*( 45 /2))";
+    let expected = 2 * 2 / (5 - 1) + 3 * (1 + 2 * (45 / 2));
+
+    assert_eq!(parser::expr.parse(data), Ok(expected));
+    assert_eq!(
+        parser_ast::expr.parse(data).map(|ast| ast.eval()),
+        Ok(expected)
+    );
+    assert_eq!(
+        parser_lexer::expr2.parse(data).map(|ast| ast.eval()),
+        Ok(expected)
+    );
+    c.bench_function("direct", |b| {
+        b.iter(|| parser::expr.parse(data).unwrap());
+    });
+    c.bench_function("ast", |b| {
+        b.iter(|| parser_ast::expr.parse(data).unwrap().eval());
+    });
+    c.bench_function("lexer", |b| {
+        b.iter(|| parser_lexer::expr2.parse_peek(data).unwrap());
+    });
+}
+
+criterion::criterion_group!(benches, arithmetic);
+criterion::criterion_main!(benches);