feat: compact boundary divider, overlay fix, approval window, PiP, Tauri enhancements

- Add CompactBoundaryDivider component for compact_boundary system messages
- Fix readability overlay: v-if removes element entirely at 0% opacity
- Add approval page and window composable
- Add PiP window support and loading screen
- Tauri: add window management commands and capabilities
- Disable Ctrl+1..5 shortcuts in Tauri (handled by global shortcuts)

src-tauri/capabilities/default.json

@@ -2,7 +2,7 @@
   "$schema": "https://raw.githubusercontent.com/tauri-apps/tauri/dev/crates/tauri-utils/schema.json",
   "identifier": "default",
   "description": "Default permissions for Agent UI",
-  "windows": ["main", "pip-terminal"],
+  "windows": ["main", "pip-terminal", "pip-terminal-1", "pip-terminal-2", "pip-terminal-3", "pip-terminal-4", "pip-terminal-5", "approval-window", "loading-window"],
   "permissions": [
     "core:default",
     {
@@ -28,9 +28,21 @@
     "core:window:allow-set-position",
     "core:window:allow-set-focus",
     "core:window:allow-set-decorations",
+    "core:window:allow-show",
+    "core:window:allow-hide",
+    "core:window:allow-inner-position",
+    "core:window:allow-inner-size",
+    "core:window:allow-outer-position",
+    "core:window:allow-outer-size",
     "core:webview:default",
     "core:webview:allow-create-webview-window",
     "core:webview:allow-webview-close",
-    "core:window:allow-destroy"
+    "core:window:allow-destroy",
+    "global-shortcut:default",
+    "global-shortcut:allow-register",
+    "global-shortcut:allow-unregister",
+    "global-shortcut:allow-is-registered",
+    "global-shortcut:allow-unregister-all",
+    "core:tray:default"
   ]
 }