docs: document YARP WithStaticFiles + WithDockerfile /wwwroot path requirement

[Copilot]

Users combining WithStaticFiles() and WithDockerfile() on a YARP resource get silent 404s because nothing documents that static files must live at /wwwroot inside the container or that the final Dockerfile stage must use the YARP base image.

Adds to the existing "Static file serving" section in the YARP integration page:

• Explanation that the YARP container expects built assets at /wwwroot
• Complete multi-stage Dockerfile example (Node.js build → YARP base image):

  FROM node:22-slim AS build
  WORKDIR /app
  COPY package*.json ./
  RUN npm ci
  COPY . .
  RUN npm run build
  
  FROM mcr.microsoft.com/dotnet/nightly/yarp
  COPY --from=build /app/dist /wwwroot

• Caution aside surfacing the The WebRootPath was not found: /wwwroot log message as a diagnostic hint

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• telemetry.astro.build
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node node /home/REDACTED/work/aspire.dev/aspire.dev/src/frontend/node_modules/.bin/../astro/astro.js dev --host 0.0.0.0 (dns block)
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node node /home/REDACTED/work/aspire.dev/aspire.dev/src/frontend/node_modules/.bin/../astro/astro.js dev --port 4322 (dns block)
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node node /home/REDACTED/work/aspire.dev/aspire.dev/src/frontend/node_modules/.bin/../astro/astro.js dev --port 4323 (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>YARP WithStaticFiles + WithDockerfile: missing docs on required /wwwroot path in Docker image</issue_title>
<issue_description>## Bug Description

When using AddYarp("frontend").WithStaticFiles().WithDockerfile("./frontend"), there is no documentation explaining that the YARP container expects static files at /wwwroot. Users must write a multi-stage Dockerfile that copies built assets to /wwwroot using the mcr.microsoft.com/dotnet/nightly/yarp base image, but this is not documented anywhere.

Current Behavior

A user creates a Dockerfile that builds frontend assets (e.g., Vite/React) but doesn't know where to place the output. The container starts successfully but returns 404 for all requests. The only clue is a log line: The WebRootPath was not found: /wwwroot. Static files may be unavailable.

Expected Behavior

The YARP integration docs should document:

1. That WithStaticFiles() expects files at /wwwroot inside the container
2. A complete example Dockerfile showing the required multi-stage build pattern, e.g.:

FROM node:22-slim AS build
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

FROM mcr.microsoft.com/dotnet/nightly/yarp
COPY --from=build /app/dist /wwwroot

3. That the Dockerfile must use the YARP base image (mcr.microsoft.com/dotnet/nightly/yarp) as its final stage so dotnet /app/yarp.dll can run

Page URL

The YARP hosting integration page (if it exists) or the general deployment docs.

Additional Context

• Aspire version: 13.3.0-pr.14149.g4bc5e9bf (all packages)
• .NET SDK: 10.0.100
• OS: macOS (Darwin arm64)
• Discovered during aspire deploy to Azure Container Apps
  </issue_description>

<agent_instructions>Please use the https://github.com/microsoft/aspire.dev/blob/main/.github/skills/doc-writer/SKILL.md skill to address issue..</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes YARP WithStaticFiles + WithDockerfile: missing docs on required /wwwroot path in Docker image #476

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.