fix(ags-v3): nice-to-have — portabilité, perf, réactivité

- Prompt.tsx: GLib.get_user_name() au lieu de hardcode "tetardtek"
- ghost-shell.desktop: $HOME au lieu de chemin absolu
- SystemStats.tsx: lecture /proc/stat + /proc/meminfo (zero fork, économie batterie)
- Battery.tsx: createDerivedBinding percentage+charging — réactif sur branchement

ags-v3/widget/modules/SystemStats.tsx

@@ -1,21 +1,50 @@
+import GLib from "gi://GLib"
 import { createPoll } from "ags/time"
-import { exec } from "ags/process"
+
+function readProc(path: string): string | null {
+  try {
+    const [ok, contents] = GLib.file_get_contents(path)
+    if (ok && contents) return new TextDecoder().decode(contents)
+  } catch {}
+  return null
+}
+
+let prevIdle = 0
+let prevTotal = 0
 
 function getCpuUsage(): string {
-  try {
-    const out = exec("bash -c \"top -bn1 | grep 'Cpu(s)' | awk '{print 100 - $8}'\"")
-    return `${Math.round(parseFloat(out))}`
-  } catch {
-    return "?"
-  }
+  const content = readProc("/proc/stat")
+  if (!content) return "?"
+
+  const line = content.split("\n")[0]  // "cpu  user nice system idle ..."
+  const parts = line.split(/\s+/).slice(1).map(Number)
+  const idle = parts[3] + parts[4]  // idle + iowait
+  const total = parts.reduce((a, b) => a + b, 0)
+
+  const dIdle = idle - prevIdle
+  const dTotal = total - prevTotal
+  prevIdle = idle
+  prevTotal = total
+
+  if (dTotal === 0) return "0"
+  return `${Math.round(((dTotal - dIdle) / dTotal) * 100)}`
 }
 
 function getRamUsage(): string {
-  try {
-    return exec("bash -c \"free | awk '/Mem:/ {printf \\\"%.0f\\\", $3/$2 * 100}'\"")
-  } catch {
-    return "?"
+  const content = readProc("/proc/meminfo")
+  if (!content) return "?"
+
+  const lines = content.split("\n")
+  let total = 0, available = 0
+
+  for (const line of lines) {
+    if (line.startsWith("MemTotal:")) total = parseInt(line.split(/\s+/)[1])
+    if (line.startsWith("MemAvailable:")) available = parseInt(line.split(/\s+/)[1])
+    if (total && available) break
   }
+
+  if (!total) return "?"
+  return `${Math.round(((total - available) / total) * 100)}`
 }
 
 export default function SystemStats() {