Address Copilot review: capitalize CPU, rename cpu_load_average

- Capitalize "cpu" to "CPU" in telemetry deprecation comment for
  consistency with existing naming conventions.
- Rename cpu_load_average to cpu_utilization to avoid confusion with
  Linux load average (which is unbounded and reported as 1/5/15 min).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: follesoe

protobuf_definitions/message_formats.proto

@@ -1368,7 +1368,7 @@ message PowerRailInfo {
 // Fields not applicable to a platform are left at their zero/empty defaults.
 message SystemPerformanceInfo {
   repeated CpuCoreLoad cpu_cores = 1; // Per-core CPU utilization.
-  float cpu_load_average = 2; // Overall CPU load (0..1).
+  float cpu_utilization = 2; // Mean CPU utilization across all cores (0..1).
   GpuInfo gpu = 3; // GPU utilization.
   repeated DlaInfo dla_engines = 4; // DLA engine utilization (Jetson only).
   MemoryInfo memory = 5; // RAM and swap usage.

protobuf_definitions/telemetry.proto

@@ -295,7 +295,7 @@ message MultibeamDiscoveryTel {
   MultibeamDiscovery discovery = 1; // Discovery data from a multibeam sonar.
 }
 
-// Information about cpu and memory usage (deprecated, use SystemPerformanceInfoTel instead).
+// Information about CPU and memory usage (deprecated, use SystemPerformanceInfoTel instead).
 message CPUInfoTel {
   CPUInfo cpu_info = 1; // CPU information.
 }