fix(security): harden avatar validation and size limits

src/agents/identity-avatar.e2e.test.ts

@@ -3,6 +3,7 @@ import os from "node:os";
 import path from "node:path";
 import { afterEach, describe, expect, it } from "vitest";
 import type { OpenClawConfig } from "../config/config.js";
+import { AVATAR_MAX_BYTES } from "../shared/avatar-policy.js";
 import { resolveAgentAvatar } from "./identity-avatar.js";
 
 async function writeFile(filePath: string, contents = "avatar") {
@@ -127,6 +128,26 @@ describe("resolveAgentAvatar", () => {
     }
   });
 
+  it("rejects local avatars larger than max bytes", async () => {
+    const root = await createTempAvatarRoot();
+    const workspace = path.join(root, "work");
+    const avatarPath = path.join(workspace, "avatars", "too-big.png");
+    await fs.mkdir(path.dirname(avatarPath), { recursive: true });
+    await fs.writeFile(avatarPath, Buffer.alloc(AVATAR_MAX_BYTES + 1));
+
+    const cfg: OpenClawConfig = {
+      agents: {
+        list: [{ id: "main", workspace, identity: { avatar: "avatars/too-big.png" } }],
+      },
+    };
+
+    const resolved = resolveAgentAvatar(cfg, "main");
+    expect(resolved.kind).toBe("none");
+    if (resolved.kind === "none") {
+      expect(resolved.reason).toBe("too_large");
+    }
+  });
+
   it("accepts remote and data avatars", () => {
     const cfg: OpenClawConfig = {
       agents: {