[docs-beta] migrate - docker agent docs (#26506)

## Summary & Motivation

Broken links converted to `/todo`:

```
  - Broken link on source page path = /dagster-plus/deployment/deployment-types/hybrid/docker/configuration:
     -> linking to /dagster-plus/deployment/agents/docker/configuring-running-docker-agent
     -> linking to /dagster-plus/managing-deployments/environment-variables-and-secrets
     -> linking to /guides/dagster/using-environment-variables-and-secrets
  - Broken link on source page path = /dagster-plus/deployment/deployment-types/hybrid/docker/setup:
     -> linking to /dagster-plus/account/managing-users
     -> linking to /dagster-plus/managing-deployments/code-locations
```

## How I Tested These Changes

## Changelog

NOCHANGELOG

docs/docs-beta/docs/dagster-plus/deployment/deployment-types/hybrid/docker/configuration.md

@@ -1,7 +1,41 @@
 ---
 title: Docker agent configuration
 sidebar_position: 200
-unlisted: true
 ---
 
-{/* TODO copy from https://docs.dagster.io/dagster-plus/deployment/agents/docker/configuration-reference */}
+:::note
+This guide is applicable to Dagster+.
+:::
+
+{/* This reference describes the various configuration options Dagster+ currently supports for [Docker agents](/dagster-plus/deployment/agents/docker/configuring-running-docker-agent). */}
+This reference describes the various configuration options Dagster+ currently supports for [Docker agents](/todo).
+
+---
+
+## Environment variables and secrets
+
+Using the `container_context.docker.env_vars` property, you can include environment variables and secrets in the Docker container associated with a specific code location. For example:
+
+```yaml
+# dagster_cloud.yaml
+locations:
+  - location_name: cloud-examples
+    image: dagster/dagster-cloud-examples:latest
+    code_source:
+      package_name: dagster_cloud_examples
+    container_context:
+      docker:
+        env_vars:
+          - DATABASE_NAME
+          - DATABASE_USERNAME=hooli_testing
+```
+
+The `container_context.docker.env_vars` property is a list, where each item can be either `KEY` or `KEY=VALUE`. If only `KEY` is specified, the value will be pulled from the local environment.
+
+Refer to the following guides for more info about environment variables:
+
+{/* - [Dagster+ environment variables and secrets](/dagster-plus/managing-deployments/environment-variables-and-secrets) */}
+- [Dagster+ environment variables and secrets](/todo)
+{/* - [Using environment variables and secrets in Dagster code](/guides/dagster/using-environment-variables-and-secrets) */}
+- [Using environment variables and secrets in Dagster code](/todo)
+

docs/docs-beta/docs/dagster-plus/deployment/deployment-types/hybrid/docker/setup.md

@@ -1,7 +1,125 @@
 ---
 title: Docker agent setup
 sidebar_position: 100
-unlisted: true
 ---
 
-{/* TODO copy from https://docs.dagster.io/dagster-plus/deployment/agents/docker/configuring-running-docker-agent */}
+:::note
+This guide is applicable to Dagster+.
+:::
+
+In this guide, you'll configure and run a Docker agent. Docker agents are used to launch your code in Docker containers.
+
+## Prerequisites
+
+To complete the steps in this guide, you'll need:
+
+{/* - **Permissions in Dagster+ that allow you to manage agent tokens**. Refer to the [User permissions documentation](/dagster-plus/account/managing-users) for more info. */}
+- **Permissions in Dagster+ that allow you to manage agent tokens**. Refer to the [User permissions documentation](/todo) for more info.
+- **To have Docker installed**
+- **Access to a container registry to which you can push images with Dagster code.** Additionally, your Docker agent must have the permissions required to pull images from the registry.
+
+  This can be:
+
+  - A self-hosted registry,
+  - A public registry such as [DockerHub](https://hub.docker.com/), or
+  - A managed offering such as [Amazon ECR](https://aws.amazon.com/ecr/), [Azure CR](https://azure.microsoft.com/en-us/services/container-registry/#overview), or [Google CR](https://cloud.google.com/container-registry)
+
+## Step 1: Generate a Dagster+ agent token
+
+In this step, you'll generate a token for the Dagster+ agent. The Dagster+ agent will use this to authenticate to the agent API.
+
+1. Sign in to your Dagster+ instance.
+2. Click the **user menu (your icon) > Organization Settings**.
+3. In the **Organization Settings** page, click the **Tokens** tab.
+4. Click the **+ Create agent token** button.
+5. After the token has been created, click **Reveal token**.
+
+Keep the token somewhere handy - you'll need it to complete the setup.
+
+## Step 2: Create a Docker agent
+
+1. Create a Docker network for your agent:
+
+   ```shell
+   docker network create dagster_cloud_agent
+   ```
+
+2. Create a `dagster.yaml` file:
+
+   ```yaml
+   instance_class:
+     module: dagster_cloud.instance
+     class: DagsterCloudAgentInstance
+
+   dagster_cloud_api:
+     agent_token: <YOUR_AGENT_TOKEN>
+     branch_deployments: true # enables branch deployments
+     deployment: prod
+
+   user_code_launcher:
+     module: dagster_cloud.workspace.docker
+     class: DockerUserCodeLauncher
+     config:
+       networks:
+         - dagster_cloud_agent
+   ```
+
+3. In the file, fill in the following:
+
+   - `agent_token` - Add the agent token you created in [Step 1](#step-1-generate-a-dagster-agent-token)
+   - `deployment` - Enter the deployment associated with this instance of the agent.
+
+     In the above example, we specified `prod` as the deployment. This is present when Dagster+ organizations are first created.
+
+4. Save the file.
+
+## Step 3: Start the agent
+
+Next, you'll start the agent as a container. Run the following command in the same folder as your `dagster.yaml` file:
+
+```shell
+docker run \
+  --network=dagster_cloud_agent \
+  --volume $PWD/dagster.yaml:/opt/dagster/app/dagster.yaml:ro \
+  --volume /var/run/docker.sock:/var/run/docker.sock \
+  -it docker.io/dagster/dagster-cloud-agent:latest \
+  dagster-cloud agent run /opt/dagster/app
+```
+
+This command:
+
+- Starts the agent with your local `dagster.yaml` mounted as a volume
+- Starts the system Docker socket mounted as a volume, allowing the agent to launch containers.
+
+To view the agent in Dagster+, click the Dagster icon in the top left to navigate to the **Status** page and click the **Agents** tab. You should see the agent running in the **Agent statuses** section:
+
+![Instance Status](/images/dagster-cloud/agents/dagster-cloud-instance-status.png)
+
+## Credential Helpers
+
+If your images are stored in a private registry, configuring a [Docker credentials helper](https://docs.docker.com/engine/reference/commandline/login/#credential-helpers) allows the agent to log in to your registry. The agent image comes with several popular credentials helpers preinstalled:
+
+- [docker-credential-ecr-login](https://github.com/awslabs/amazon-ecr-credential-helper)
+- [docker-credential-gcr](https://github.com/GoogleCloudPlatform/docker-credential-gcr)
+
+These credential helpers generally are configured in `~/.docker.config.json`. To use one, make sure you mount that file as a volume when you start your agent:
+
+```shell
+  docker run \
+    --network=dagster_cloud_agent \
+    --volume $PWD/dagster.yaml:/opt/dagster/app/dagster.yaml:ro \
+    --volume /var/run/docker.sock:/var/run/docker.sock \
+    --volume ~/.docker/config.json:/root/.docker/config.json:ro \
+    -it docker.io/dagster/dagster-cloud-agent:latest \
+    dagster-cloud agent run /opt/dagster/app
+```
+
+## Next steps
+
+Now that you've got your agent running, what's next?
+
+{/* - **If you're getting Dagster+ set up**, the next step is to [add a code location](/dagster-plus/managing-deployments/code-locations) using the agent. */}
+- **If you're getting Dagster+ set up**, the next step is to [add a code location](/todo) using the agent.
+
+{/* - **If you're ready to load your Dagster code**, refer to the [Adding Code to Dagster+](/dagster-plus/managing-deployments/code-locations) guide for more info. */}
+- **If you're ready to load your Dagster code**, refer to the [Adding Code to Dagster+](/todo) guide for more info.