feat(skills/settings): 技能复制 + 设置持久化等会话前改动

- 技能复制:新增 POST 复制接口(_rewrite_skill_frontmatter_name 重写 frontmatter name + 校验 + 去重),前端 skills api/hooks 与技能设置页配套
- 设置持久化:lastAgentId、线程 RAG 模式锁(settings/index、local)
- i18n(en/zh/types)、agent-card/input-box/message-list 等页面文案与交互微调
- scheduler/element.py 小修

(本批为会话前已存在的工作区改动,按要求一并提交;构建产物 backend.zip 未提交)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend-web/src/pages/AgentChatPage.tsx

@@ -26,7 +26,7 @@ import { useAgent } from "@/core/agents";
 import { useI18n } from "@/core/i18n/hooks";
 import { useModels } from "@/core/models/hooks";
 import { useNotification } from "@/core/notification/hooks";
-import { useThreadSettings } from "@/core/settings";
+import { saveLastAgentId, useThreadSettings } from "@/core/settings";
 import { useThreadStream } from "@/core/threads/hooks";
 import { textOfMessage } from "@/core/threads/utils";
 import { env } from "@/env";
@@ -114,6 +114,9 @@ export default function AgentChatPage() {
   const handleSubmit = useCallback(
     (message: PromptInputMessage) => {
       setHasStartedConversation(true);
+      // Remember this agent so the new-chat landing screen pre-selects it next
+      // time (covers both direct agent chats and the ChatPage handoff replay).
+      saveLastAgentId(agent_id);
       window.dispatchEvent(
         new CustomEvent("workspace:sandbox-resume-autoscroll"),
       );
@@ -216,6 +219,7 @@ export default function AgentChatPage() {
                 paddingBottom={messageListPaddingBottom}
                 tokenUsageEnabled={tokenUsageEnabled}
                 onClarificationSubmit={handleClarificationSubmit}
+                onEditResubmit={(text) => handleSubmit({ text, files: [] })}
               />
             </div>
 

frontend-web/src/pages/ChatPage.tsx

@@ -23,10 +23,15 @@ import { ThreadTitle } from "@/components/workspace/thread-title";
 import { TodoList } from "@/components/workspace/todo-list";
 import { TokenUsageIndicator } from "@/components/workspace/token-usage-indicator";
 import { Welcome } from "@/components/workspace/welcome";
+import { useAgentSelector } from "@/core/agents";
 import { useI18n } from "@/core/i18n/hooks";
 import { useModels } from "@/core/models/hooks";
 import { useNotification } from "@/core/notification/hooks";
-import { useThreadSettings } from "@/core/settings";
+import {
+  getLastAgentId,
+  saveLastAgentId,
+  useThreadSettings,
+} from "@/core/settings";
 import { useThreadStream } from "@/core/threads/hooks";
 import { useRouteBase } from "@/core/route-base";
 import { textOfMessage } from "@/core/threads/utils";
@@ -47,6 +52,8 @@ export default function ChatPage() {
   const { data: promptPrefixSettings } = usePromptPrefixSettings();
   const [promptPrefixOn, setPromptPrefixOn] = useState(false);
   const [selectedAgentId, setSelectedAgentId] = useState<string | null>(null);
+  const { agents: selectorAgents, isLoading: selectorLoading } =
+    useAgentSelector();
   const { selectedArtifact } = useArtifacts();
   useSpecificChatMode();
 
@@ -58,10 +65,22 @@ export default function ChatPage() {
     if (isNewThread) {
       setHasStartedConversation(false);
       setPromptPrefixOn(false);
-      setSelectedAgentId(null);
+      // Pre-select the agent the user last started a conversation with so a
+      // fresh chat defaults to it. Validated against the selector list below.
+      setSelectedAgentId(getLastAgentId());
     }
   }, [isNewThread, threadId]);
 
+  // Drop a restored last-used agent that is no longer in the selector list
+  // (deleted / unpublished / no longer curated), so we never hand off to a
+  // dead agent. Wait for the list to load before deciding.
+  useEffect(() => {
+    if (selectorLoading || !selectedAgentId) return;
+    if (!selectorAgents.some((a) => a.id === selectedAgentId)) {
+      setSelectedAgentId(null);
+    }
+  }, [selectedAgentId, selectorAgents, selectorLoading]);
+
   const { showNotification } = useNotification();
 
   const [thread, sendMessage, isUploading] = useThreadStream({
@@ -184,6 +203,14 @@ export default function ChatPage() {
     },
     [sendMessage, threadId],
   );
+
+  // Persist the picked agent the moment it changes so the next new chat
+  // defaults to it — even if the user never sends a message this session.
+  // Passing null (the ✕ clear) wipes the stored preference.
+  const handleAgentChange = useCallback((agentId: string | null) => {
+    setSelectedAgentId(agentId);
+    saveLastAgentId(agentId);
+  }, []);
   const handleStop = useCallback(async () => {
     await thread.stop();
   }, [thread]);
@@ -248,6 +275,9 @@ export default function ChatPage() {
                   paddingBottom={messageListPaddingBottom}
                   tokenUsageEnabled={tokenUsageEnabled}
                   onClarificationSubmit={handleClarificationSubmit}
+                  onEditResubmit={(text) =>
+                    handleSubmit({ text, files: [] })
+                  }
                 />
               )}
             </div>
@@ -305,7 +335,7 @@ export default function ChatPage() {
                         isLandingState
                           ? {
                               selectedAgentId,
-                              onAgentChange: setSelectedAgentId,
+                              onAgentChange: handleAgentChange,
                             }
                           : undefined
                       }

frontend-web/src/pages/NewAgentPage.tsx

@@ -545,13 +545,13 @@ export default function NewAgentPage() {
                         没有匹配的技能。
                       </p>
                     ) : (
-                      <div className="flex flex-wrap gap-2">
+                      <div className="grid grid-cols-1 gap-2 sm:grid-cols-2">
                         {filteredSkills.map((skill) => {
                           const checked = selectedSkills.includes(skill.name);
                           return (
                             <div
                               key={skill.name}
-                              className="inline-flex max-w-full items-center"
+                              className="flex w-full min-w-0 items-center"
                             >
                               <Button
                                 type="button"
@@ -560,7 +560,7 @@ export default function NewAgentPage() {
                                 onClick={() => toggleSkill(skill)}
                                 title={skill.description}
                                 className={cn(
-                                  "h-8 max-w-[200px] rounded-r-none",
+                                  "h-8 min-w-0 flex-1 rounded-r-none",
                                   !checked && "text-muted-foreground",
                                 )}
                               >