fix: stabilize AI coach chat against truncation and empty replies

Co-authored-by: Cursor <cursoragent@cursor.com>

manual_trading_hub/static/app.css

@@ -4327,6 +4327,10 @@ body.hub-page-ai #page-ai {
   font-style: italic;
   animation: ai-think-pulse 1.2s ease-in-out infinite;
 }
+.ai-bubble-error {
+  border-color: color-mix(in srgb, var(--red) 55%, var(--border-soft));
+  color: var(--red);
+}
 @keyframes ai-think-pulse {
   0%,
   100% {

manual_trading_hub/static/app.js

@@ -990,10 +990,7 @@
       btn.classList.toggle("is-active", on);
       btn.setAttribute("aria-selected", on ? "true" : "false");
     });
-    if (mobile && active === "chat") {
-      const box = document.getElementById("ai-chat-messages");
-      if (box) requestAnimationFrame(() => { box.scrollTop = box.scrollHeight; });
-    }
+    if (mobile && active === "chat") scrollAiChatToEnd();
   }
 
   function initAiMobileTabs() {
@@ -3271,12 +3268,34 @@
     ].join("");
   }
 
+  function scrollAiChatToEnd() {
+    const box = document.getElementById("ai-chat-messages");
+    if (!box) return;
+    const run = () => {
+      box.scrollTop = box.scrollHeight;
+      const rows = box.querySelectorAll(".ai-msg-row");
+      const last = rows[rows.length - 1];
+      if (last && last.scrollIntoView) {
+        try {
+          last.scrollIntoView({ block: "end", behavior: "auto" });
+        } catch (_) {
+          /* ignore */
+        }
+      }
+    };
+    requestAnimationFrame(() => requestAnimationFrame(run));
+  }
+
   function renderAiChatRow(role, content, extraClass, attachments) {
     const isUser = role === "user";
     const label = isUser ? "主人" : "AI教练";
     const rowCls = isUser ? "ai-msg-row-user" : "ai-msg-row-coach";
     const bubbleCls = isUser ? "ai-bubble-user" : "ai-bubble-assistant";
     const isThinking = extraClass && String(extraClass).includes("ai-bubble-thinking");
+    const isError =
+      !isUser &&
+      !isThinking &&
+      /^(AI 调用失败|AI 生成失败)/.test(String(content || "").trim());
     const bubbleInner = isUser || isThinking ? esc(content || "") : renderHubMarkdown(content || "");
     const mdCls = !isUser && !isThinking ? " ai-result-md" : "";
     const attList = Array.isArray(attachments) ? attachments : [];
@@ -3289,7 +3308,7 @@
       `<div class="ai-msg-row ${rowCls}">` +
       `<span class="ai-msg-role">${label}</span>` +
       `${attHtml}` +
-      `<div class="ai-bubble ${bubbleCls}${mdCls}${extraClass ? " " + extraClass : ""}">${bubbleInner}</div>` +
+      `<div class="ai-bubble ${bubbleCls}${mdCls}${isError ? " ai-bubble-error" : ""}${extraClass ? " " + extraClass : ""}">${bubbleInner}</div>` +
       `</div>`
     );
   }
@@ -3327,7 +3346,7 @@
       html += renderAiChatRow("assistant", "正在思考…", "ai-bubble-thinking");
     }
     box.innerHTML = html;
-    box.scrollTop = box.scrollHeight;
+    scrollAiChatToEnd();
   }
 
   function setAiChatBusy(busy) {
@@ -3452,7 +3471,11 @@
       }
     } catch (e) {
       showToast(String(e), true);
-      renderAiChatMessages(aiChatSessionCache);
+      try {
+        await loadAiChatSession();
+      } catch (_) {
+        renderAiChatMessages(aiChatSessionCache);
+      }
     } finally {
       setAiChatBusy(false);
     }