[BUG] Slack Channel Not Found

**Describe the bug**
The Slack integration seems to not be able to handle private channels, it can get triggered but the API fails when it is time to send a reply to a private channel

**To Reproduce**
1. Create a slack integration to a private channel
2. Use it in a workflow

1. Create a automation that is triggered by a text from a private channel
2. Test it by triggering the agent
3. Agent gets triggered but cannot respond back into the channel

**Expected behavior**
Ability to send and receive messages in a private channel

**Screenshots**
If applicable, add screenshots to help explain your problem. Note that the screenshots will be displayed publicly.



**Additional context**

Here is the error message I got back in my debugger logs

{
"name": "ToolError$UnhandledToolError",
"agentMessage": "An API error occurred: channel_not_found",
"userMessage": "An API error occurred: channel_not_found",
"blocks": [
{
"type": "{#system:hint#}",
"text": "An API error occurred: channel_not_found",
"label": "error-with-hint",
"ephemeral": false
}
],
"events": [],
"extraSentryTags": null,
"canAgentSelfHeal": true,
"captureWithSentry": true,
"shouldDisableTrigger": false,
"retryable": true,
"errorCategory": "unexpected",
"message": "An unhandled error occurred during tool execution:\nAn API error occurred: channel_not_found",
"stack": "ToolError$UnhandledToolError: An unhandled error occurred during tool execution:\nAn API error occurred: channel_not_found\n at file:///usr/src/app/packages/core/dist/agent/tools/toolRegistry/analytics/index.js:107:23\n at process.processTicksAndRejections (node:internal/process/task_queues:95:5)\n at async withActionAnalytics (file:///usr/src/app/packages/core/dist/agent/tools/toolRegistry/analytics/index.js:15:12)\n at async wrapActionCall (file:///usr/src/app/packages/core/dist/agent/tools/toolRegistry/actionCallWrappers.js:18:24)\n at async ActionDefinition.callAsAgentV2 (file:///usr/src/app/packages/core/dist/agent/tools/toolRegistry/ActionDefinition.js:654:24)\n at async AgentCore.streamActionCall (file:///usr/src/app/packages/core/dist/tasks/framework/agent/AgentCore.js:121:24)",
"cause": {
"code": "slack_webapi_platform_error",
"data": {
"ok": false,
"error": "channel_not_found",
"response_metadata": {
"scopes": [
"incoming-webhook",
"users:read",
"chat:write",
"chat:write.public",
"im:write",
"mpim:write",
"channels:join",
"chat:write.customize",
"channels:write.topic",
"groups:write.topic",
"mpim:write.topic",
"im:write.topic"
],
"acceptedScopes": [
"chat:write"
]
}
},
"name": "Error",
"message": "An API error occurred: channel_not_found",
"stack": "Error: **An API error occurred: channel_not_found**\n at platformErrorFromResult (/usr/src/app/node_modules/.pnpm/@slack+web-api@6.9.0/node_modules/@slack/web-api/dist/errors.js:56:33)\n at WebClient.apiCall (/usr/src/app/node_modules/.pnpm/@slack+web-api@6.9.0/node_modules/@slack/web-api/dist/WebClient.js:181:56)\n at process.processTicksAndRejections (node:internal/process/task_queues:95:5)\n at async sendSlackMessage (file:///usr/src/app/packages/core/dist/agent/tools/slack/lib/sendMessage.js:97:35)\n at async SlackThreadChannel.streamReply (file:///usr/src/app/packages/core/dist/agent/tools/slack/channels/SlackThreadChannel.js:97:29)\n at async SlackThreadChannel.streamAgentMessageAsActionCall (file:///usr/src/app/packages/core/dist/agent/tools/slack/channels/SlackThreadChannel.js:112:9)\n at async file:///usr/src/app/packages/core/dist/agent/tools/toolRegistry/actionFactories/createChannel.js:75:28\n at async ActionDefinition.callActionFinal (file:///usr/src/app/packages/core/dist/agent/tools/toolRegistry/ActionDefinition.js:887:41)\n at async ActionDefinition.callAsAgentV2Internal (file:///usr/src/app/packages/core/dist/agent/tools/toolRegistry/ActionDefinition.js:803:16)\n at async ExecutionContext.withCancelledGuard (file:///usr/src/app/packages/core/dist/tasks/framework/contexts/executionContext.js:260:16)\n at async withErrorCoercion (file:///usr/src/app/packages/core/dist/agent/tools/toolRegistry/errorHandling/index.js:9:16)\n at async withActionRateLimitInterrupts (file:///usr/src/app/packages/core/dist/agent/tools/toolRegistry/actionCallWrappers.js:162:16)\n at async runWithHTTPInterceptors (file:///usr/src/app/packages/lib/dist/backend/httpInterceptors/httpInterceptors.js:29:20)\n at async withHttpTracing (file:///usr/src/app/packages/core/dist/agent/tools/toolRegistry/actionCallWrappers.js:94:24)\n at async withAgentFacingLogs (file:///usr/src/app/packages/core/dist/agent/tools/toolsLib/agentFacingLog.js:8:12)\n at async file:///usr/src/app/packages/core/dist/agent/tools/toolRegistry/analytics/index.js:47:22\n at async withActionAnalytics (file:///usr/src/app/packages/core/dist/agent/tools/toolRegistry/analytics/index.js:15:12)\n at async wrapActionCall (file:///usr/src/app/packages/core/dist/agent/tools/toolRegistry/actionCallWrappers.js:18:24)\n at async ActionDefinition.callAsAgentV2 (file:///usr/src/app/packages/core/dist/agent/tools/toolRegistry/ActionDefinition.js:654:24)\n at async AgentCore.streamActionCall (file:///usr/src/app/packages/core/dist/tasks/framework/agent/AgentCore.js:121:24)"
}
}