slack: add regression test for read threadId forwarding

Covers actions.handleAction(read) -> handleSlackAction(readMessages) including threadId.

extensions/slack/src/channel.read-threadid.test.ts

@@ -0,0 +1,48 @@
+import { describe, expect, it, vi } from "vitest";
+
+import { slackPlugin } from "./channel.js";
+import { setSlackRuntime } from "./runtime.js";
+
+import type { MoltbotConfig } from "../../../src/config/config.js";
+import { createPluginRuntime } from "../../../src/plugins/runtime/index.js";
+
+describe("slack plugin read action", () => {
+  it("forwards threadId to readMessages", async () => {
+    const runtime = createPluginRuntime();
+
+    const handleSlackAction = vi.fn(async () => ({ ok: true }));
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    (runtime.channel.slack as any).handleSlackAction = handleSlackAction;
+
+    setSlackRuntime(runtime);
+
+    const cfg = {
+      channels: {
+        slack: {
+          botToken: "xoxb-test",
+          appToken: "xapp-test",
+        },
+      },
+    } as MoltbotConfig;
+
+    await slackPlugin.actions.handleAction({
+      action: "read",
+      params: {
+        channelId: "C123",
+        threadId: "1712345678.000100",
+        limit: 3,
+      },
+      cfg,
+      accountId: undefined,
+      toolContext: undefined,
+    });
+
+    expect(handleSlackAction).toHaveBeenCalledTimes(1);
+    expect(handleSlackAction.mock.calls[0]?.[0]).toMatchObject({
+      action: "readMessages",
+      channelId: "C123",
+      limit: 3,
+      threadId: "1712345678.000100",
+    });
+  });
+});