fix(metrics): simplify macOS memory to use Node.js os module

.github/copilot-instructions.md

@@ -57,7 +57,7 @@ fix(collector): prevent memory leak in long-running processes
 docs(readme): update installation instructions
 refactor(renderer): simplify chart generation logic
 test(metrics): add tests for drift compensation
-chore(deps): update systeminformation to v5.22.0
+refactor(metrics): replace systeminformation with native OS commands
 ci(workflow): add Node.js 24 to test matrix
 perf(post): optimize metrics file reading
 ```

CLAUDE.md

@@ -24,7 +24,7 @@ Examples:
 - `feat(metrics): add memory pressure tracking`
 - `fix(collector): prevent memory leak in long-running processes`
 - `docs(readme): update installation instructions`
-- `chore(deps): update systeminformation to v5.22.0`
+- `refactor(metrics): replace systeminformation with native OS commands`
 
 See `.github/copilot-instructions.md` for complete guidelines.
 
@@ -64,8 +64,9 @@ npm test                       # Run all tests
 ### Key Components
 
 - **src/lib.ts**: Shared utilities and data schemas for metrics collection.
+- **src/system-info.ts**: Native system information collector for CPU, memory, and disk metrics. All metrics use platform-specific commands for accuracy. CPU: Linux `/proc/stat`, macOS `top`, Windows PowerShell. Memory: Linux `/proc/meminfo`, macOS/Windows Node.js `os` module. Disk: Linux/macOS `df`, Windows PowerShell.
 - **src/main/metrics.ts**: Collects CPU (user/system 0-100%) and memory (active/available in MB).
-  Uses `systeminformation`. Starts collection in constructor with drift-compensated `setTimeout`.
+  Uses native OS commands via `system-info.ts`. Starts collection in constructor with drift-compensated `setTimeout`.
   Stores data in memory only; calls `saveState()` on stop.
 - **src/main/collector.ts**: Simple background process that creates a Metrics instance and keeps running.
   Ensures `stop()` is called on SIGTERM/SIGINT to save metrics state.
@@ -102,7 +103,7 @@ before(async () => {
   mock.timers.enable({ apis: ['setTimeout', 'Date'] });
 
   // Mock other modules
-  mockModule = mock.module("systeminformation", { /* ... */ });
+  mockModule = mock.module("../system-info.ts", { /* ... */ });
 
   // Import after mocking
   ({ Metrics } = await import("./metrics.ts"));
@@ -119,7 +120,7 @@ for (let i = 0; i < 5; i++) {
 
 ```typescript
 // Mock the module before importing
-mock.module("systeminformation", {
+mock.module("../system-info.ts", {
   namedExports: {
     currentLoad: async () =>
       Promise.resolve({

README.md

@@ -237,7 +237,7 @@ src/
 
 1. `src/main/index.ts` is executed
 2. Node.js spawns `src/main/collector.ts` as a detached background process
-3. `Metrics` class collects CPU/memory/disk information every 5 seconds using `systeminformation` library
+3. `Metrics` class collects CPU/memory/disk information every 5 seconds using native OS commands
 4. Metrics data is stored in memory only (no disk writes during collection)
 5. On process termination (SIGTERM/SIGINT), metrics are saved to GitHub Actions state