fix(telegram): ignore message_thread_id for non-forum group sessions

Regular Telegram groups (without Topics/Forums enabled) can send
message_thread_id when users reply to messages. This was incorrectly
being used to create separate session keys like '-123:topic:42',
causing each reply chain to get its own conversation context.

Now resolveTelegramForumThreadId only returns a thread ID when the
chat is actually a forum (is_forum=true). For regular groups, the
thread ID is ignored, ensuring all messages share the same session.

DMs continue to use messageThreadId for thread sessions as before.

src/telegram/bot-message-context.dm-threads.test.ts

@@ -70,3 +70,102 @@ describe("buildTelegramMessageContext dm thread sessions", () => {
     expect(ctx?.ctxPayload?.SessionKey).toBe("agent:main:main");
   });
 });
+
+describe("buildTelegramMessageContext group sessions without forum", () => {
+  const baseConfig = {
+    agents: { defaults: { model: "anthropic/claude-opus-4-5", workspace: "/tmp/clawd" } },
+    channels: { telegram: {} },
+    messages: { groupChat: { mentionPatterns: [] } },
+  } as never;
+
+  const buildContext = async (message: Record<string, unknown>) =>
+    await buildTelegramMessageContext({
+      primaryCtx: {
+        message,
+        me: { id: 7, username: "bot" },
+      } as never,
+      allMedia: [],
+      storeAllowFrom: [],
+      options: { forceWasMentioned: true },
+      bot: {
+        api: {
+          sendChatAction: vi.fn(),
+          setMessageReaction: vi.fn(),
+        },
+      } as never,
+      cfg: baseConfig,
+      account: { accountId: "default" } as never,
+      historyLimit: 0,
+      groupHistories: new Map(),
+      dmPolicy: "open",
+      allowFrom: [],
+      groupAllowFrom: [],
+      ackReactionScope: "off",
+      logger: { info: vi.fn() },
+      resolveGroupActivation: () => true,
+      resolveGroupRequireMention: () => false,
+      resolveTelegramGroupConfig: () => ({
+        groupConfig: { requireMention: false },
+        topicConfig: undefined,
+      }),
+    });
+
+  it("ignores message_thread_id for regular groups (not forums)", async () => {
+    // When someone replies to a message in a non-forum group, Telegram sends
+    // message_thread_id but this should NOT create a separate session
+    const ctx = await buildContext({
+      message_id: 1,
+      chat: { id: -1001234567890, type: "supergroup", title: "Test Group" },
+      date: 1700000000,
+      text: "@bot hello",
+      message_thread_id: 42, // This is a reply thread, NOT a forum topic
+      from: { id: 42, first_name: "Alice" },
+    });
+
+    expect(ctx).not.toBeNull();
+    // Session key should NOT include :topic:42
+    expect(ctx?.ctxPayload?.SessionKey).toBe("agent:main:telegram:group:-1001234567890");
+    // MessageThreadId should be undefined (not a forum)
+    expect(ctx?.ctxPayload?.MessageThreadId).toBeUndefined();
+  });
+
+  it("keeps same session for regular group with and without message_thread_id", async () => {
+    const ctxWithThread = await buildContext({
+      message_id: 1,
+      chat: { id: -1001234567890, type: "supergroup", title: "Test Group" },
+      date: 1700000000,
+      text: "@bot hello",
+      message_thread_id: 42,
+      from: { id: 42, first_name: "Alice" },
+    });
+
+    const ctxWithoutThread = await buildContext({
+      message_id: 2,
+      chat: { id: -1001234567890, type: "supergroup", title: "Test Group" },
+      date: 1700000001,
+      text: "@bot world",
+      from: { id: 42, first_name: "Alice" },
+    });
+
+    expect(ctxWithThread).not.toBeNull();
+    expect(ctxWithoutThread).not.toBeNull();
+    // Both messages should use the same session key
+    expect(ctxWithThread?.ctxPayload?.SessionKey).toBe(ctxWithoutThread?.ctxPayload?.SessionKey);
+  });
+
+  it("uses topic session for forum groups with message_thread_id", async () => {
+    const ctx = await buildContext({
+      message_id: 1,
+      chat: { id: -1001234567890, type: "supergroup", title: "Test Forum", is_forum: true },
+      date: 1700000000,
+      text: "@bot hello",
+      message_thread_id: 99,
+      from: { id: 42, first_name: "Alice" },
+    });
+
+    expect(ctx).not.toBeNull();
+    // Session key SHOULD include :topic:99 for forums
+    expect(ctx?.ctxPayload?.SessionKey).toBe("agent:main:telegram:group:-1001234567890:topic:99");
+    expect(ctx?.ctxPayload?.MessageThreadId).toBe(99);
+  });
+});