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/document-features/CHANGELOG.md

@@ -0,0 +1,62 @@
+# Changelog
+
+## 0.2.12 - 2025-10-24
+
+* Update litrs dependency to 1.0.0
+
+## 0.2.11 - 2025-02-16
+
+* Collect defaults recursively (#19)
+
+## 0.2.10 - 2024-07-12
+
+* Revert parsing of multi-lines string while parsing features
+  (Keep parsing of multi-lines string when detecting if we need to use Cargo.toml.orig)
+
+## 0.2.9 - 2024-07-11
+
+* Fix parsing of multi-lines string (#25)
+* Fix `out_of_scope_macro_calls` compatibility warning
+* Fix documentation having too many `#` (#22)
+
+## 0.2.8 - 2023-12-29
+
+* Remove `\n` between features (#17)
+* Don't throw an error when there is no features in Cargo.toml (#20)
+
+## 0.2.7 - 2022-12-21
+
+* Fix parsing of Cargo.toml with multi-line array of array (#16)
+
+## 0.2.6 - 2022-09-24
+
+* Fix parsing of escaped string literal in the macro arguments
+
+## 0.2.5 - 2022-09-17
+
+* Allow customization of the output with the `feature_label=` parameter
+
+## 0.2.4 - 2022-09-14
+
+* Fix dependencies or features written with quotes
+
+## 0.2.3 - 2022-08-15
+
+* Fix parsing of table with `#` within strings (#10)
+
+## 0.2.2 - 2022-07-25
+
+* Fix parsing of dependencies or feature spanning multiple lines (#9)
+
+## 0.2.1 - 2022-02-12
+
+* Fix indentation of multi-lines feature comments (#5)
+
+## 0.2.0 - 2022-02-11
+
+* Added ability to document optional features. (This is a breaking change in the
+  sense that previously ignored comments may now result in errors)
+
+## 0.1.0 - 2022-02-01
+
+Initial release