fix: route clear canvas requests through confirmation

lib/canvas/agent-model-planner.ts

@@ -136,7 +136,13 @@ function getDecisionNodeIds(params: {
 
 function inferHighRiskOperation(userText: string) {
   const text = userText.toLowerCase();
-  if (/删除|删掉|移除/.test(text)) return "delete_nodes";
+  if (
+    /删除|删掉|删了|删去|移除/.test(text) ||
+    /清空(?:画布|选中|当前|节点|对象|元素|这些|全部)/.test(text) ||
+    /清除(?:选中|当前|节点|对象|元素|这些|全部)/.test(text)
+  ) {
+    return "delete_nodes";
+  }
   if (/覆盖|替换当前|替换原图|直接替换|覆盖原图/.test(text)) {
     return "replace_node_media";
   }

tests/routes/canvas-chat-helpers.test.ts

@@ -266,6 +266,12 @@ test.describe("canvas chat pure helpers", () => {
         context: plannerContext,
       })
     ).toBe(true);
+    expect(
+      shouldConsiderCanvasAgentModelPlanner({
+        userText: "清空选中的节点",
+        context: plannerContext,
+      })
+    ).toBe(true);
   });
 
   test("treats selected agent slots as canvas routing context", () => {
@@ -656,6 +662,23 @@ test.describe("canvas chat pure helpers", () => {
       riskOperation: "delete_nodes",
       targetNodeIds: ["image-1", "text-1"],
     });
+
+    const clearOutcome = normalizeCanvasAgentModelPlannerDecision({
+      decision: {
+        action: "none",
+      },
+      context: plannerContext,
+      projectId: plannerContext.projectId || "",
+      messageId: "message-1",
+      chatId: "chat-1",
+      userText: "清除选中的对象",
+    });
+
+    expect(clearOutcome).toMatchObject({
+      kind: "confirmation_required",
+      riskOperation: "delete_nodes",
+      targetNodeIds: ["image-1", "text-1"],
+    });
   });
 
   test("builds pending move-node operation from model-planned high-risk layout", () => {