fix(ai): constrain explain plan canvas overflow

apps/desktop/src/components/editor/AiAssistant.vue

@@ -2614,8 +2614,8 @@ async function openExternalUrl(url: string) {
                         <GitBranch class="h-3 w-3" />
                         {{ t("explain.title") }}
                       </Button>
-                      <div v-if="step.toolName === 'explain_query' && step.explainData && connection?.db_type" class="mb-1">
-                        <ExplainPlanViewer :plan="parseExplainFromData(step.explainData, connection.db_type)" class="max-h-64" />
+                      <div v-if="step.toolName === 'explain_query' && step.explainData && connection?.db_type" class="mb-1 h-64 overflow-hidden rounded border">
+                        <ExplainPlanViewer :plan="parseExplainFromData(step.explainData, connection.db_type)" />
                       </div>
                       <div v-else-if="step.isError && step.toolResult" class="text-[10px] text-red-600 dark:text-red-400">{{ step.toolResult }}</div>
                       <div v-else-if="step.toolResult" class="max-h-48 overflow-auto text-[10px] text-muted-foreground whitespace-pre-wrap">{{ step.toolResult }}</div>

apps/desktop/src/components/editor/__tests__/AiAssistant.explainPlanContainment.spec.ts

@@ -0,0 +1,18 @@
+import { readFileSync } from "node:fs";
+import { describe, expect, it } from "vitest";
+
+const source = readFileSync(new URL("../AiAssistant.vue", import.meta.url), "utf8");
+
+describe("AI assistant explain_query canvas containment", () => {
+  it("bounds the embedded ExplainPlanViewer to a fixed, clipped height", () => {
+    const match = source.match(/<div v-if="step\.toolName === 'explain_query' && step\.explainData[^>]*class="([^"]*)"/);
+    expect(match, "explain_query wrapper div not found").not.toBeNull();
+    const wrapperClass = match![1];
+    expect(wrapperClass).toContain("h-64");
+    expect(wrapperClass).toContain("overflow-hidden");
+  });
+
+  it("does not rely on an unresolvable max-height alone to contain the canvas", () => {
+    expect(source).not.toContain('<ExplainPlanViewer :plan="parseExplainFromData(step.explainData, connection.db_type)" class="max-h-64" />');
+  });
+});