fix: cherry-pick PR#94 improvements + dashboard loading fix

- ws-client: connection dedup (_connecting state), connect() guard, global singleton
- chat: 8 null guards (sendMessage/doSend/createStreamBubble/renderAttachments/showPageGuide/loadHistory)
- chat: auto-scroll control (wheel/touch/scrollBtn, disable on scroll-up)
- chat: tool call rendering (appendToolsToEl, collectToolsFromMessage, upsertTool, mergeToolEventData)
- chat: tool event tracking (agent tool events -> _toolEventData/_toolRunIndex)
- chat: extractChatContent/extractContent/dedupeHistory full tools support
- chat.css: .msg-tool collapsible card styles
- dashboard: .catch() on loadDashboardData fire-and-forget, error state + retry button

src/style/chat.css

@@ -855,6 +855,55 @@
   color: var(--text-tertiary);
 }
 
+/* 工具调用 */
+.msg-tool {
+  margin-bottom: 8px;
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+.msg-tool-item {
+  border: 1px solid var(--border-primary, var(--border));
+  background: var(--bg-tertiary, var(--bg-secondary));
+  border-radius: var(--radius-md, 8px);
+  padding: 8px 10px;
+}
+.msg-tool-item > summary {
+  cursor: pointer;
+  font-size: 12px;
+  color: var(--text-secondary);
+  list-style: none;
+}
+.msg-tool-item > summary::-webkit-details-marker {
+  display: none;
+}
+.msg-tool-body {
+  margin-top: 8px;
+  display: none;
+  gap: 8px;
+}
+.msg-tool-item[open] > .msg-tool-body {
+  display: grid;
+}
+.msg-tool-block {
+  background: var(--bg-primary, var(--bg));
+  border: 1px solid var(--border-primary, var(--border));
+  border-radius: var(--radius-sm, 4px);
+  padding: 8px 10px;
+}
+.msg-tool-title {
+  font-size: 11px;
+  color: var(--text-tertiary);
+  margin-bottom: 6px;
+}
+.msg-tool-block pre {
+  margin: 0;
+  white-space: pre-wrap;
+  word-break: break-word;
+  font-size: 11px;
+  color: var(--text-primary);
+}
+
 /* 首次引导提示 */
 .chat-page-guide {
   margin: 0 16px 8px;