fix: 新建会话时强制中断生成并恢复发送按钮

- startNewSession() 中 abort 正在进行的流式请求
- 重置 IS_STREAMING = false, ABORT_CONTROLLER = null
- 强制恢复发送按钮图标和状态

src/renderer/main.ts

@@ -128,6 +128,23 @@ async function startNewSession(): Promise<void> {
   const session = createNewSession();
   state.set(KEYS.CURRENT_SESSION, session);
   logInfo('新建会话');
+
+  // ── 强制中断正在进行的生成 ──
+  const abortController = state.get<AbortController | null>(KEYS.ABORT_CONTROLLER);
+  if (abortController) {
+    abortController.abort();
+  }
+  state.set(KEYS.IS_STREAMING, false);
+  state.set(KEYS.ABORT_CONTROLLER, null);
+
+  // ── 恢复发送按钮 ──
+  const btnSend = document.querySelector('#btnSend') as HTMLButtonElement;
+  if (btnSend) {
+    btnSend.innerHTML = `<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><line x1="22" y1="2" x2="11" y2="13"/><polygon points="22 2 15 22 11 13 2 9 22 2"/></svg>`;
+    btnSend.classList.remove('stop-btn', 'disabled');
+    btnSend.title = '发送';
+  }
+
   state.set(KEYS.IS_HISTORY_VIEW, false);
 
   (document.querySelector('#historyBar') as HTMLElement).style.display = 'none';