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/xtensa-lx-rt/CHANGELOG.md

@@ -0,0 +1,36 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## Unreleased
+
+### Added
+
+### Changed
+
+### Fixed
+
+### Removed
+
+## 0.17.2 - 2024-11-20
+
+### Fixed
+
+- Fixed saving the state of the FPU co-processor. (#2311)
+
+### Removed
+
+## 0.17.1 - 2024-09-02
+
+### Added
+
+- Better diagnostics when using floats inside an interrupt handler when using the default hard fault handler (#2044)
+
+### Fixed
+
+- Store state of FP coprocessor in stack memory (#2057)
+
+## Initial releases