fix(agent-bot): Include payload in webhook retry failure logs (#13879)

Webhook retry failure logs for agent-bot now include the event payload,
making it easier to identify which event failed when debugging transient
upstream errors (429/500).

Previously the log only showed:
`[AgentBots::WebhookJob] attempt 1 failed
RestClient::InternalServerError`

Now it includes the payload:
`[AgentBots::WebhookJob] attempt 1 failed
RestClient::InternalServerError payload={"event":"message_created",...}`

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/jobs/agent_bots/webhook_job.rb

@@ -8,7 +8,7 @@ class AgentBots::WebhookJob < WebhookJob
   def perform(url, payload, webhook_type = :agent_bot_webhook)
     super(url, payload, webhook_type)
   rescue RestClient::TooManyRequests, RestClient::InternalServerError => e
-    Rails.logger.warn("[AgentBots::WebhookJob] attempt #{executions} failed #{e.class.name}")
+    Rails.logger.warn("[AgentBots::WebhookJob] attempt #{executions} failed #{e.class.name} payload=#{payload.to_json}")
     raise
   end
 end