Document linux/amd64-only Docker architecture

Update documentation to reflect that Sandbox SDK now builds Docker
images for linux/amd64 only to ensure dev/prod parity.

Changes:
- Add architecture compatibility section to docker-setup partial
- Clarify that ARM Mac users will use automatic emulation
- Update Dockerfile reference to note linux/amd64 architecture
- Explain dev/prod parity benefits

Related to cloudflare/sandbox-sdk#245

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Co-Authored-By: Claude <[email protected]>

Author: github-actions[bot]

src/content/docs/sandbox/configuration/dockerfile.mdx

@@ -25,13 +25,17 @@ See [Version compatibility](/sandbox/concepts/sandboxes/#version-compatibility)
 
 **What's included:**
 
-- Ubuntu 22.04 LTS base
+- Ubuntu 22.04 LTS base (linux/amd64 architecture)
 - Python 3.11.14 with pip and venv
 - Node.js 20 LTS with npm
 - Bun 1.x (JavaScript/TypeScript runtime)
 - Pre-installed Python packages: matplotlib, numpy, pandas, ipython
 - System utilities: curl, wget, git, jq, zip, unzip, file, procps, ca-certificates
 
+:::note[Architecture]
+Images are built for **linux/amd64 only** to match Cloudflare's production container runtime. ARM Mac users will automatically use emulation (Rosetta/QEMU) for local development, ensuring perfect dev/prod parity.
+:::
+
 ## Creating a custom image
 
 Create a `Dockerfile` in your project root:

src/content/partials/containers/docker-setup.mdx

@@ -2,3 +2,9 @@ You must have Docker running locally when you run `wrangler deploy`. For most pe
 
 You can check that Docker is running properly by running the `docker info` command in your terminal. If Docker is running, the command will succeed. If Docker is not running,
 the `docker info` command will hang or return an error including the message "Cannot connect to the Docker daemon".
+
+## Architecture compatibility
+
+Sandbox SDK builds Docker images for **linux/amd64 only**, matching Cloudflare's production container runtime. This ensures dev/prod parity and prevents architecture-specific bugs.
+
+**On ARM Macs (Apple Silicon)**: Docker automatically uses emulation (Rosetta/QEMU) when running amd64 images. This is expected behavior and ensures your local environment matches production exactly. You may notice slightly slower container startup during development, but this guarantees your code behaves identically in production.