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/Battery.tsx

@@ -1,29 +1,38 @@
 import AstalBattery from "gi://AstalBattery"
-import { createBinding } from "ags"
+import { createBinding, createDerivedBinding } from "ags"
 
 export default function Battery() {
   const bat = AstalBattery.get_default()
 
-  const text = createBinding(bat, "percentage")((p: number) => {
-    const pct = Math.round(p * 100)
-    let icon = ""
-    if (bat.charging) icon = "󰂄"
-    else if (pct > 90) icon = "󰁹"
-    else if (pct > 70) icon = "󰂁"
-    else if (pct > 50) icon = "󰁿"
-    else if (pct > 30) icon = "󰁽"
-    else if (pct > 10) icon = "󰁻"
-    else icon = "󰂃"
-    return `${icon} ${pct}%`
-  })
+  const percentage = createBinding(bat, "percentage")
+  const charging = createBinding(bat, "charging")
 
-  const cls = createBinding(bat, "percentage")((p: number) => {
-    const pct = Math.round(p * 100)
-    if (bat.charging) return "battery charging"
-    if (pct <= 10) return "battery low"
-    if (pct <= 20) return "battery warning"
-    return "battery"
-  })
+  const text = createDerivedBinding(
+    [percentage, charging],
+    (p: number, isCharging: boolean) => {
+      const pct = Math.round(p * 100)
+      let icon = ""
+      if (isCharging) icon = "󰂄"
+      else if (pct > 90) icon = "󰁹"
+      else if (pct > 70) icon = "󰂁"
+      else if (pct > 50) icon = "󰁿"
+      else if (pct > 30) icon = "󰁽"
+      else if (pct > 10) icon = "󰁻"
+      else icon = "󰂃"
+      return `${icon} ${pct}%`
+    },
+  )
+
+  const cls = createDerivedBinding(
+    [percentage, charging],
+    (p: number, isCharging: boolean) => {
+      const pct = Math.round(p * 100)
+      if (isCharging) return "battery charging"
+      if (pct <= 10) return "battery low"
+      if (pct <= 20) return "battery warning"
+      return "battery"
+    },
+  )
 
   return <label class={cls} label={text} />
 }