feat(ui): add hover effects to window control buttons

Add hover background and text color changes to minimize, maximize, and close buttons in the header bar for better visual feedback. The close button now turns red on hover for clearer destructive action indication.

Remove backup package.json file and add comprehensive agent system development plan document (agents.md) detailing architecture analysis and implementation roadmap.

src/components/HeaderBar/index.vue

@@ -6,14 +6,16 @@
 
     <div class="title-bar-controls w-[168px] flex items-center justify-end text-tx-secondary">
       <native-tooltip :content="t('window.minimize')">
-        <button v-show="isMinimizable" class="flex items-center justify-center cursor-pointer w-[40px] h-[40px]"
+        <button v-show="isMinimizable"
+          class="flex items-center justify-center cursor-pointer w-[40px] h-[40px] hover:bg-[#999] hover:text-[#fff]"
           @click="minimizeWindow">
           <iconify-icon icon="material-symbols:check-indeterminate-small" :color="color" :width="btnSize"
             :height="btnSize" />
         </button>
       </native-tooltip>
       <native-tooltip :content="isMaximized ? t('window.restore') : t('window.maximize')">
-        <button v-show="isMaximizable" class="flex items-center justify-center cursor-pointer w-[40px] h-[40px]"
+        <button v-show="isMaximizable"
+          class="flex items-center justify-center cursor-pointer w-[40px] h-[40px] hover:bg-[#999] hover:text-[#fff]"
           @click="maximizeWindow">
           <iconify-icon icon="material-symbols:chrome-maximize-outline-sharp" :color="color" :width="btnSize"
             :height="btnSize" v-show="!isMaximized" />
@@ -22,7 +24,8 @@
         </button>
       </native-tooltip>
       <native-tooltip :content="t('window.close')">
-        <button v-show="isClosable" class="flex items-center justify-center cursor-pointer w-[40px] h-[40px]"
+        <button v-show="isClosable"
+          class="flex items-center justify-center cursor-pointer w-[40px] h-[40px] hover:bg-[#ff0000] hover:text-[#fff]"
           @click="handleClose">
           <iconify-icon icon="material-symbols:close" :color="color" :width="btnSize" :height="btnSize" />
         </button>