refactor(chat): remove keyboard compatibility layer

src/app/chat/components/chat-input-bar.module.css

@@ -1,14 +1,11 @@
 /* ChatInputBar 输入栏容器样式（与 Dart chat_input_bar.dart 对齐） */
 
-/* 键盘适配：--chat-input-lift 仅写入当前聊天输入栏。 */
-
 .bar {
   flex: 0 0 auto;
   padding: 0
     calc(var(--chat-inline-padding, 16px) + var(--app-safe-right, 0px))
     calc(
-      var(--spacing-lg, 16px) + var(--chat-input-lift, 0px) +
-        var(--app-safe-bottom, 0px)
+      var(--spacing-lg, 16px) + var(--app-safe-bottom, 0px)
     )
     calc(var(--chat-inline-padding, 16px) + var(--app-safe-left, 0px));
   background: transparent;

src/app/chat/components/chat-input-bar.tsx

@@ -4,7 +4,7 @@ import { useRef, useState } from "react";
 import { useChatDispatch } from "@/stores/chat/chat-context";
 import { Logger } from "@/utils/logger";
 
-import { useChatKeyboardAvoidance } from "../hooks/use-chat-keyboard-avoidance";
+import { useChatKeyboardDiagnostics } from "../hooks/use-chat-keyboard-diagnostics";
 import { ChatInputTextField } from "./chat-input-text-field";
 import { ChatSendButton } from "./chat-send-button";
 import styles from "./chat-input-bar.module.css";
@@ -26,10 +26,7 @@ export function ChatInputBar({ disabled = false }: ChatInputBarProps) {
 
   const hasContent = input.trim().length > 0;
 
-  useChatKeyboardAvoidance({
-    containerRef: barRef,
-    active: isFocused,
-  });
+  useChatKeyboardDiagnostics({ containerRef: barRef });
 
   const handleInputChange = (value: string) => {
     setInput(value);