feat: display macOS battery capacity and cached memory, and refine status view presentation

cmd/status/metrics_memory.go

@@ -3,6 +3,7 @@ package main
 import (
 	"context"
 	"runtime"
+	"strconv"
 	"strings"
 	"time"
 
@@ -18,16 +19,62 @@ func collectMemory() (MemoryStatus, error) {
 	swap, _ := mem.SwapMemory()
 	pressure := getMemoryPressure()
 
+	// On macOS, vm.Cached is 0, so we calculate from file-backed pages.
+	cached := vm.Cached
+	if runtime.GOOS == "darwin" && cached == 0 {
+		cached = getFileBackedMemory()
+	}
+
 	return MemoryStatus{
 		Used:        vm.Used,
 		Total:       vm.Total,
 		UsedPercent: vm.UsedPercent,
 		SwapUsed:    swap.Used,
 		SwapTotal:   swap.Total,
+		Cached:      cached,
 		Pressure:    pressure,
 	}, nil
 }
 
+func getFileBackedMemory() uint64 {
+	ctx, cancel := context.WithTimeout(context.Background(), 500*time.Millisecond)
+	defer cancel()
+	out, err := runCmd(ctx, "vm_stat")
+	if err != nil {
+		return 0
+	}
+
+	// Parse page size from first line: "Mach Virtual Memory Statistics: (page size of 16384 bytes)"
+	var pageSize uint64 = 4096 // Default
+	lines := strings.Split(out, "\n")
+	if len(lines) > 0 {
+		firstLine := lines[0]
+		if strings.Contains(firstLine, "page size of") {
+			if _, after, found := strings.Cut(firstLine, "page size of "); found {
+				if before, _, found := strings.Cut(after, " bytes"); found {
+					if size, err := strconv.ParseUint(strings.TrimSpace(before), 10, 64); err == nil {
+						pageSize = size
+					}
+				}
+			}
+		}
+	}
+
+	// Parse "File-backed pages: 388975."
+	for _, line := range lines {
+		if strings.Contains(line, "File-backed pages:") {
+			if _, after, found := strings.Cut(line, ":"); found {
+				numStr := strings.TrimSpace(after)
+				numStr = strings.TrimSuffix(numStr, ".")
+				if pages, err := strconv.ParseUint(numStr, 10, 64); err == nil {
+					return pages * pageSize
+				}
+			}
+		}
+	}
+	return 0
+}
+
 func getMemoryPressure() string {
 	if runtime.GOOS != "darwin" {
 		return ""