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/zerocopy/ci/check_job_dependencies.sh

@@ -0,0 +1,35 @@
+#!/usr/bin/env bash
+#
+# Copyright 2024 The Fuchsia Authors
+#
+# Licensed under a BSD-style license <LICENSE-BSD>, Apache License, Version 2.0
+# <LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0>, or the MIT
+# license <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your option.
+# This file may not be copied, modified, or distributed except according to
+# those terms.
+
+set -eo pipefail
+which yq > /dev/null
+jobs=$(for i in $(find .github -iname '*.yaml' -or -iname '*.yml')
+  do
+    # Select jobs that are triggered by pull request.
+    if yq -e '.on | has("pull_request")' "$i" 2>/dev/null >/dev/null
+    then
+      # This gets the list of jobs that all-jobs-succeed does not depend on.
+      comm -23 \
+        <(yq -r '.jobs | keys | .[]' "$i" | sort | uniq) \
+        <(yq -r '.jobs["all-jobs-succeed"].needs[]' "$i" | sort | uniq)
+    fi
+
+  # The grep call here excludes all-jobs-succeed from the list of jobs that
+  # all-jobs-succeed does not depend on.  If all-jobs-succeed does
+  # not depend on itself, we do not care about it.
+  done | sort | uniq | (grep -v '^all-jobs-succeed$' || true)
+)
+
+if [ -n "$jobs" ]
+then
+  missing_jobs="$(echo "$jobs" | tr ' ' '\n')"
+  echo "all-jobs-succeed missing dependencies on some jobs: $missing_jobs" | tee -a $GITHUB_STEP_SUMMARY >&2
+  exit 1
+fi