feat(ags-v3): brain HUD terminal — kitty toggle + single instance + COSMIC window rule

- BrainPower panel: dashboard only (VTE embed pas compatible AGS JSX)
- toggle-brain.sh: ouvre/ferme panel AGS + terminal Kitty (single instance via pgrep)
- Kitty class brain-hud-terminal pour COSMIC window rule (floating)
- app.ts: cleanup focusBrainTerm removed
- style.scss: brain-terminal class + brain-commits-list

ags-v3/style.scss

@@ -124,4 +124,11 @@ window.BrainPower {
     font-family: "Maple Mono NF", monospace;
     padding: 4px 0 4px 16px;
   }
+
+  .brain-terminal {
+    background: #1a0e27;
+    border-radius: 0 0 $radius 0;
+    padding: 4px;
+    min-height: 400px;
+  }
 }