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/pulldown-cmark/tests/suite/gfm_strikethrough.rs

@@ -0,0 +1,37 @@
+// This file is auto-generated by the build script
+// Please, do not modify it manually
+
+use super::test_markdown_html;
+
+#[test]
+fn gfm_strikethrough_test_1() {
+    let original = r##"~~Hi~~ Hello, ~there~ world!
+"##;
+    let expected = r##"<p><del>Hi</del> Hello, <del>there</del> world!</p>
+"##;
+
+    test_markdown_html(original, expected, false, false, false);
+}
+
+#[test]
+fn gfm_strikethrough_test_2() {
+    let original = r##"This ~~has a
+
+new paragraph~~.
+"##;
+    let expected = r##"<p>This ~~has a</p>
+<p>new paragraph~~.</p>
+"##;
+
+    test_markdown_html(original, expected, false, false, false);
+}
+
+#[test]
+fn gfm_strikethrough_test_3() {
+    let original = r##"This will ~~~not~~~ strike.
+"##;
+    let expected = r##"<p>This will ~~~not~~~ strike.</p>
+"##;
+
+    test_markdown_html(original, expected, false, false, false);
+}