refactor: unify threading contexts

src/slack/threading.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect, it } from "vitest";
 
-import { resolveSlackThreadTargets } from "./threading.js";
+import { resolveSlackThreadContext, resolveSlackThreadTargets } from "./threading.js";
 
 describe("resolveSlackThreadTargets", () => {
   it("threads replies when message is already threaded", () => {
@@ -45,4 +45,35 @@ describe("resolveSlackThreadTargets", () => {
     expect(replyThreadTs).toBeUndefined();
     expect(statusThreadTs).toBe("123");
   });
+
+  it("sets messageThreadId for top-level messages when replyToMode is all", () => {
+    const context = resolveSlackThreadContext({
+      replyToMode: "all",
+      message: {
+        type: "message",
+        channel: "C1",
+        ts: "123",
+      },
+    });
+
+    expect(context.isThreadReply).toBe(false);
+    expect(context.messageThreadId).toBe("123");
+    expect(context.replyToId).toBe("123");
+  });
+
+  it("prefers thread_ts as messageThreadId for replies", () => {
+    const context = resolveSlackThreadContext({
+      replyToMode: "off",
+      message: {
+        type: "message",
+        channel: "C1",
+        ts: "123",
+        thread_ts: "456",
+      },
+    });
+
+    expect(context.isThreadReply).toBe(true);
+    expect(context.messageThreadId).toBe("456");
+    expect(context.replyToId).toBe("456");
+  });
 });