docs: add --slack-full-width documentation

Add docs for the new --slack-full-width CLI flag that enables
full-width Slack alerts with Markdown test result tables.

Made-with: Cursor

Author: haritamar

docs/oss/deployment-and-configuration/slack.mdx

@@ -57,3 +57,15 @@ The alert format is:
 ```
 
 ---
+
+## Full-width alerts
+
+By default, Slack alerts use a narrower layout with some content in attachments. To use the full message width and show test results as a Markdown table in the main message body, pass the flag when running the monitor:
+
+```shell
+edr monitor --slack-token <your_slack_token> --slack-channel-name <channel> --slack-full-width
+```
+
+With `--slack-full-width`, alerts are sent using Slack Block Kit in the main message body instead of attachments, so the full channel width is used and test result samples appear as formatted Markdown tables.
+
+---

docs/oss/guides/alerts/send-slack-alerts.mdx

@@ -28,6 +28,8 @@ Make sure to run the following command after your dbt runs and tests:
 edr monitor --slack-token <your_slack_token> --slack-channel-name <slack_channel_to_post_at> --group-by [table | alert]
 ```
 
+Add `--slack-full-width` to use the full message width and show test results as Markdown tables. See [Slack setup - Full-width alerts](/oss/deployment-and-configuration/slack#full-width-alerts).
+
 Or just `edr monitor` if you used `config.yml`. Please note that when you specify the --slack-channel-name, it's the
 default channel name to which all the alerts will be sent that are not attributed to any custom channel. Therefore,
 if you execute several `edr monitor` commands at the same time with different `slack-channel-name` arguments, they can