feat(agents): configurable default runTimeoutSeconds for subagent spawns

When sessions_spawn is called without runTimeoutSeconds, subagents
previously defaulted to 0 (no timeout). This adds a config key at
agents.defaults.subagents.runTimeoutSeconds so operators can set a
global default timeout for all subagent runs.

The agent-provided value still takes precedence when explicitly passed.
When neither the agent nor the config specifies a timeout, behavior is
unchanged (0 = no timeout), preserving backwards compatibility.

Updated for the subagent-spawn.ts refactor (logic moved from
sessions-spawn-tool.ts to spawnSubagentDirect).

Closes #19288

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/agents/openclaw-tools.subagents.sessions-spawn-default-timeout-absent.test.ts

@@ -0,0 +1,69 @@
+import { describe, expect, it, vi } from "vitest";
+import { createSessionsSpawnTool } from "./tools/sessions-spawn-tool.js";
+
+vi.mock("../config/config.js", async () => {
+  const actual = await vi.importActual("../config/config.js");
+  return {
+    ...actual,
+    loadConfig: () => ({
+      agents: {
+        defaults: {
+          subagents: {
+            maxConcurrent: 8,
+          },
+        },
+      },
+      routing: {
+        sessions: {
+          mainKey: "agent:test:main",
+        },
+      },
+    }),
+  };
+});
+
+vi.mock("../gateway/call.js", () => {
+  return {
+    callGateway: vi.fn(async ({ method }: { method: string }) => {
+      if (method === "agent") {
+        return { runId: "run-456" };
+      }
+      return {};
+    }),
+  };
+});
+
+vi.mock("../plugins/hook-runner-global.js", () => ({
+  getGlobalHookRunner: () => null,
+}));
+
+type GatewayCall = { method: string; params?: Record<string, unknown> };
+
+async function getGatewayCalls(): Promise<GatewayCall[]> {
+  const { callGateway } = await import("../gateway/call.js");
+  return (callGateway as unknown as ReturnType<typeof vi.fn>).mock.calls.map(
+    (call) => call[0] as GatewayCall,
+  );
+}
+
+function findLastCall(calls: GatewayCall[], predicate: (call: GatewayCall) => boolean) {
+  for (let i = calls.length - 1; i >= 0; i -= 1) {
+    const call = calls[i];
+    if (call && predicate(call)) {
+      return call;
+    }
+  }
+  return undefined;
+}
+
+describe("sessions_spawn default runTimeoutSeconds (config absent)", () => {
+  it("falls back to 0 (no timeout) when config key is absent", async () => {
+    const tool = createSessionsSpawnTool({ agentSessionKey: "agent:test:main" });
+    const result = await tool.execute("call-1", { task: "hello" });
+    expect(result.details).toMatchObject({ status: "accepted" });
+
+    const calls = await getGatewayCalls();
+    const agentCall = findLastCall(calls, (call) => call.method === "agent");
+    expect(agentCall?.params?.timeout).toBe(0);
+  });
+});