feat(slack): add dm-specific replyToMode configuration (#1442)

Adds support for separate replyToMode settings for DMs vs channels:

- Add channels.slack.dm.replyToMode for DM-specific threading
- Keep channels.slack.replyToMode as default for channels
- Add resolveSlackReplyToMode helper to centralize logic
- Pass chatType through threading resolution chain

Usage:
```json5
{
  channels: {
    slack: {
      replyToMode: "off",     // channels
      dm: {
        replyToMode: "all"    // DMs always thread
      }
    }
  }
}
```

When dm.replyToMode is set, DMs use that mode; channels use the
top-level replyToMode. Backward compatible when not configured.

src/slack/accounts.ts

@@ -107,3 +107,13 @@ export function listEnabledSlackAccounts(cfg: ClawdbotConfig): ResolvedSlackAcco
     .map((accountId) => resolveSlackAccount({ cfg, accountId }))
     .filter((account) => account.enabled);
 }
+
+export function resolveSlackReplyToMode(
+  account: ResolvedSlackAccount,
+  chatType?: string | null,
+): "off" | "first" | "all" {
+  if (chatType === "direct" && account.dm?.replyToMode !== undefined) {
+    return account.dm.replyToMode;
+  }
+  return account.replyToMode ?? "off";
+}

src/slack/threading-tool-context.test.ts

@@ -0,0 +1,96 @@
+import { describe, expect, it } from "vitest";
+
+import type { ClawdbotConfig } from "../config/config.js";
+import { buildSlackThreadingToolContext } from "./threading-tool-context.js";
+
+const emptyCfg = {} as ClawdbotConfig;
+
+describe("buildSlackThreadingToolContext", () => {
+  it("uses top-level replyToMode by default", () => {
+    const cfg = {
+      channels: {
+        slack: { replyToMode: "first" },
+      },
+    } as ClawdbotConfig;
+    const result = buildSlackThreadingToolContext({
+      cfg,
+      accountId: null,
+      context: { ChatType: "channel" },
+    });
+    expect(result.replyToMode).toBe("first");
+  });
+
+  it("uses dm.replyToMode for direct messages when configured", () => {
+    const cfg = {
+      channels: {
+        slack: {
+          replyToMode: "off",
+          dm: { replyToMode: "all" },
+        },
+      },
+    } as ClawdbotConfig;
+    const result = buildSlackThreadingToolContext({
+      cfg,
+      accountId: null,
+      context: { ChatType: "direct" },
+    });
+    expect(result.replyToMode).toBe("all");
+  });
+
+  it("uses top-level replyToMode for channels even when dm.replyToMode is set", () => {
+    const cfg = {
+      channels: {
+        slack: {
+          replyToMode: "off",
+          dm: { replyToMode: "all" },
+        },
+      },
+    } as ClawdbotConfig;
+    const result = buildSlackThreadingToolContext({
+      cfg,
+      accountId: null,
+      context: { ChatType: "channel" },
+    });
+    expect(result.replyToMode).toBe("off");
+  });
+
+  it("falls back to top-level when dm.replyToMode is not set", () => {
+    const cfg = {
+      channels: {
+        slack: {
+          replyToMode: "first",
+          dm: { enabled: true },
+        },
+      },
+    } as ClawdbotConfig;
+    const result = buildSlackThreadingToolContext({
+      cfg,
+      accountId: null,
+      context: { ChatType: "direct" },
+    });
+    expect(result.replyToMode).toBe("first");
+  });
+
+  it("uses all mode when ThreadLabel is present", () => {
+    const cfg = {
+      channels: {
+        slack: { replyToMode: "off" },
+      },
+    } as ClawdbotConfig;
+    const result = buildSlackThreadingToolContext({
+      cfg,
+      accountId: null,
+      context: { ChatType: "channel", ThreadLabel: "some-thread" },
+    });
+    expect(result.replyToMode).toBe("all");
+  });
+
+  it("defaults to off when no replyToMode is configured", () => {
+    const result = buildSlackThreadingToolContext({
+      cfg: emptyCfg,
+      accountId: null,
+      context: { ChatType: "direct" },
+    });
+    expect(result.replyToMode).toBe("off");
+  });
+});

src/slack/threading-tool-context.ts

@@ -3,7 +3,7 @@ import type {
   ChannelThreadingToolContext,
 } from "../channels/plugins/types.js";
 import type { ClawdbotConfig } from "../config/config.js";
-import { resolveSlackAccount } from "./accounts.js";
+import { resolveSlackAccount, resolveSlackReplyToMode } from "./accounts.js";
 
 export function buildSlackThreadingToolContext(params: {
   cfg: ClawdbotConfig;
@@ -11,11 +11,11 @@ export function buildSlackThreadingToolContext(params: {
   context: ChannelThreadingContext;
   hasRepliedRef?: { value: boolean };
 }): ChannelThreadingToolContext {
-  const configuredReplyToMode =
-    resolveSlackAccount({
-      cfg: params.cfg,
-      accountId: params.accountId,
-    }).replyToMode ?? "off";
+  const account = resolveSlackAccount({
+    cfg: params.cfg,
+    accountId: params.accountId,
+  });
+  const configuredReplyToMode = resolveSlackReplyToMode(account, params.context.ChatType);
   const effectiveReplyToMode = params.context.ThreadLabel ? "all" : configuredReplyToMode;
   const threadId = params.context.MessageThreadId ?? params.context.ReplyToId;
   return {