feat: replace Linux FFI with pure Dart cgroup implementation

[thiagoalmeidasa]

Summary

• Replace Linux native FFI bindings with a pure Dart implementation that reads cgroup v1/v2 files directly, eliminating glibc dependencies and enabling gVisor compatibility
• Keep macOS FFI with pre-built dylibs (macOS has no cgroup equivalent)
• Simplify CI by removing Linux native binary builds; only macOS binaries are rebuilt automatically

What's included

• Pure Dart cgroup readers: CpuMonitor (CPU accounting via cpu.stat / cpuacct.usage), MemoryMonitor (memory via memory.current / memory.usage_in_bytes), with /proc/loadavg and /proc/meminfo fallbacks for non-container Linux hosts
• Platform detection: PlatformDetector with DetectedPlatform enum (macOS, linuxCgroupV2, linuxCgroupV1, linuxHost, unsupported) for flat single-switch dispatch across all SystemResources methods
• Cgroup path resolution: Parses /proc/self/cgroup to resolve the process's actual cgroup v2 directory, fixing memory metrics on native Linux hosts where memory.max/memory.current don't exist at root
• macOS FFI wrapper: MacOsNative class isolating all FFI bindings, loaded only when running on macOS
• CPU normalization fix: getLoad() now delegates to getLimitCores() for the full fallback chain (cgroup limit -> SYSRES_CPU_CORES env var -> Platform.numberOfProcessors), fixing ~50% underreporting in gVisor
• Domain-oriented naming: Renamed files and classes from implementation names to domain names (cgroup_cpu -> cpu_monitor, cgroup_memory -> memory_monitor, cgroup_detector -> platform_detector, macos_ffi -> macos_native)
• CI simplification: Merged binary rebuild into main CI workflow; Linux tests no longer need make or native compilation

Usage

import 'package:system_resources_2/system_resources_2.dart';

void main() async {
  // Initialize (required for macOS FFI, no-op on Linux)
  await SystemResources.init();

  // Container detection
  print('Container: ${SystemResources.isContainerEnv()}');
  print('Cgroup version: ${SystemResources.cgroupVersion()}');

  // CPU metrics (auto-detects container limits)
  print('CPU Load: ${(SystemResources.cpuLoadAvg() * 100).toStringAsFixed(1)}%');
  print('CPU Limit: ${SystemResources.cpuLimitCores()} cores');

  // Memory metrics (auto-detects container limits)
  print('Memory Usage: ${(SystemResources.memUsage() * 100).toStringAsFixed(1)}%');
  print('Memory Limit: ${SystemResources.memoryLimitBytes() ~/ 1024 ~/ 1024} MB');
  print('Memory Used: ${SystemResources.memoryUsedBytes() ~/ 1024 ~/ 1024} MB');
}

Test plan

• dart test passes on macOS (arm64 and Intel)
• dart test passes on Linux (amd64 and arm64)
• Container tests pass with --memory and --cpus limits (cgroup v2)
• CpuMonitor unit tests verify limit resolution fallback chain
• CI green on all matrix targets (native + container)

[github-actions]

macOS Binaries Rebuilt

The macOS native binaries have been automatically rebuilt from source.
Linux uses pure Dart implementation (no native binaries needed).

MD5 Checksums

6a52408a4a06a0639d7a124318696260  libsysres-darwin-arm64.dylib
a3e7bfe372642d42c02cfe43b832019d  libsysres-darwin-x86_64.dylib

These checksums can be used to verify the provenance of the binaries.