Follow-up: update official documentation for App Service container deployment

PR #8847 adds container image deployment support to the built-in App Service service target (host: appservice). When a service is configured with language: docker (or docker.path), azd now builds and pushes the image to ACR and updates the site's linuxFxVersion to point at the image, enabling Web App for Containers scenarios.

The PR already updated the in-repo schema reference (docs/reference/azure-yaml-schema.md and schemas/). This issue tracks updating the official azd documentation (Microsoft Learn / azure-dev-docs) to reflect the new capability.

Docs to update

• Supported languages / hosts matrix — note that host: appservice now supports container (language: docker / docker.path) deployments, Linux only.
• azure.yaml schema/reference pages — document the App Service container mode and the docker block usage for appservice.
• App Service how-to / hosting guidance — document the Web App for Containers flow with an example azure.yaml.

Important behaviors to document (decisions made during PR review)

• azd deploy only updates the image reference (linuxFxVersion = DOCKER|<image>). It does not configure infrastructure. The site must already be provisioned as a Linux container app via IaC (bicep/terraform), including kind: linux, a DOCKER| linuxFxVersion, and ACR access (e.g. acrUseManagedIdentityCreds). azd deploy validates this and returns an actionable error if the site is not container-ready.
• Linux only in this initial implementation (no Windows containers).
• Single container only (no multi-container / docker-compose).
• ACR auth via managed identity, configured in IaC (admin credentials not supported).
• Note any differences from the containerapp target so users moving workloads between hosts understand what does/doesn't carry over (e.g. service-level env: handling, polyglot containerization), per the final decisions in feat: support container deployment to App Service #8847.

Related

• Implemented by: feat: support container deployment to App Service #8847
• Original feature request: Support deployment of containers to App Service #1608