v1.2.0: 优化移动端输入与代码块显示体验

修复代码块长内容导致的页面横向溢出，并将移动端回车默认行为调整为换行，避免误触发送，提升手机端可用性。

public/style.css

@@ -337,6 +337,7 @@ body {
 .messages {
   flex: 1;
   overflow-y: auto;
+  overflow-x: hidden;
   padding: 16px;
   display: flex;
   flex-direction: column;
@@ -368,6 +369,7 @@ body {
   display: flex;
   gap: 10px;
   max-width: 85%;
+  min-width: 0;
   animation: fadeIn 0.25s ease;
 }
 @keyframes fadeIn {
@@ -396,6 +398,8 @@ body {
   border-radius: 16px;
   line-height: 1.65;
   word-break: break-word;
+  min-width: 0;
+  max-width: 100%;
 }
 .msg.user .msg-bubble {
   background: var(--bg-bubble-user);
@@ -480,6 +484,7 @@ body {
   border-radius: 10px;
   overflow: hidden;
   border: 1px solid var(--border-color);
+  max-width: 100%;
 }
 .code-block-header {
   display: flex;
@@ -504,12 +509,15 @@ body {
   margin: 0;
   padding: 12px;
   overflow-x: auto;
+  overflow-y: hidden;
+  max-width: 100%;
   -webkit-overflow-scrolling: touch;
 }
 .code-block-wrapper pre code {
   font-family: 'SF Mono', 'Fira Code', 'Cascadia Code', monospace;
   font-size: 13px;
   line-height: 1.5;
+  white-space: pre;
 }
 
 /* Tool calls */
@@ -655,6 +663,7 @@ body {
   outline: none;
   max-height: var(--input-max-height);
   min-height: 24px;
+  overflow-y: auto;
 }
 #msg-input::placeholder { color: var(--text-muted); }
 .send-btn, .abort-btn {