fix(slack): bound inbound media downloads

docs/gateway/config-channels.md

@@ -390,6 +390,11 @@ WhatsApp runs through the gateway's web channel (Baileys Web). It starts automat
       enabled: true,
       botToken: "xoxb-...",
       appToken: "xapp-...",
+      socketMode: {
+        clientPingTimeout: 15000,
+        serverPingTimeout: 30000,
+        pingPongLoggingEnabled: false,
+      },
       dmPolicy: "pairing",
       allowFrom: ["U123", "U456", "*"],
       dm: { enabled: true, groupEnabled: false, groupChannels: ["G123"] },
@@ -448,6 +453,7 @@ WhatsApp runs through the gateway's web channel (Baileys Web). It starts automat
 
 - **Socket mode** requires both `botToken` and `appToken` (`SLACK_BOT_TOKEN` + `SLACK_APP_TOKEN` for default account env fallback).
 - **HTTP mode** requires `botToken` plus `signingSecret` (at root or per-account).
+- `socketMode` passes Slack SDK Socket Mode transport tuning through to the public Bolt receiver API. Use it only when investigating ping/pong timeout or stale websocket behavior.
 - `botToken`, `appToken`, `signingSecret`, and `userToken` accept plaintext
   strings or SecretRef objects.
 - Slack account snapshots expose per-credential source/status fields such as