Set up agent instructions (#426)

* Add agent instructions
* Update README metadata for docfx installation process
---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: TimHess <3947063+TimHess@users.noreply.github.com>
Co-authored-by: Tim Hess <tim.hess@broadcom.com>

Author: Copilot

AGENTS.md

@@ -0,0 +1,44 @@
+# Agent instructions for Steeltoe Documentation
+
+## Scope and constraints
+
+- **This repo is primarily documentation.** Prefer minimal, surgical edits. Do not change application or build code unless the task explicitly requires it.
+- **When editing docs only:** do not modify `.github/workflows/` or `src/`.
+- **Version focus:** Steeltoe v4 is current; v2 and v3 are legacy. Prefer v4 paths and examples unless the task targets an older version.
+
+## Do / Don't
+
+| Do | Don't |
+| --- | --- |
+| Use `.md` extensions for internal links | Use `.html` in internal links |
+| Run the docfx build (see [README.md](README.md)) before committing doc changes; fix `InvalidFileLink` and similar warnings | Commit doc changes without validating |
+| Add new pages to the relevant `toc.yml` (see [docs/README.md](docs/README.md)) | Add new API version config without updating `build/metadata.conf` and the corresponding build API config files |
+| Use [docfx Flavored Markdown](https://dotnet.github.io/docfx/docs/markdown.html) | Change Blazor or workflow files unless the task explicitly requires it |
+
+## Where to find instructions
+
+**Use the READMEs as the source of truth.** Update them when build or content steps change; AGENTS.md only points to them.
+
+- **[README.md](README.md)** — Build order, commands to run the site locally, clean build (`git clean -xdff`). Run docfx before `dotnet run` or you get 404s and `InvalidFileLink` from `docs/api`.
+- **[build/README.md](build/README.md)** — API Browser: script, version/source switches, what the script does.
+- **[docs/README.md](docs/README.md)** — docfx layout, links and cross-references, YAML front matter options, creating blog posts and doc pages (including `toc.yml` examples).
+
+## Overview and layout
+
+This repository hosts the [Steeltoe website](https://steeltoe.io/): documentation and blog articles, built with ASP.NET Core Blazor and docfx. Key locations:
+
+- **`docs/`** — Content (see [docs/README.md](docs/README.md) for subdirs and content rules).
+- **`src/Steeltoe.io/`** — Blazor app; docfx output goes to `wwwroot`.
+- **`build/`** — API Browser script and config ([build/README.md](build/README.md)).
+- **CI** — `.github/workflows/build-and-stage.yml`.
+
+## Linting and config
+
+- Markdown: `.markdownlint.json`
+- Editor: `.editorconfig`
+
+## Resources
+
+- **Canonical instructions:** [README.md](README.md), [build/README.md](build/README.md), [docs/README.md](docs/README.md).
+- [docfx documentation](https://dotnet.github.io/docfx) · [docfx Flavored Markdown](https://dotnet.github.io/docfx/docs/markdown.html)
+- [Steeltoe website](https://steeltoe.io) · [ASP.NET Core Blazor](https://learn.microsoft.com/aspnet/core/blazor/)

build/README.md

@@ -22,7 +22,7 @@ This process can take a while to complete, will display many warnings and may in
 
 ## What does the script do?
 
-1. Install docfx (by running `dotnet tool restore`, which installs tools defined in [dotnet-tools.json](../.config/dotnet-tools.json))
+1. Download docfx binaries (temporary workaround for .NET 10 support)
 1. Clone several copies of Steeltoe (using [metadata.conf](./metadata.conf) to identify checkout targets)
 1. Run `docfx metadata api-v{version}.json` for each copy
    1. This command will produce many yaml files and place them in [docs](../docs), alongside the index pages for each API version

docs/README.md

@@ -14,7 +14,7 @@ If you are working with API Browser content, view [this README](../build/README.
 
 ## Installing docfx
 
-Install docfx by running `dotnet tool restore`, which installs tools defined in [dotnet-tools.json](../.config/dotnet-tools.json).
+docfx is automatically downloaded by the [build-metadata.ps1](../build/build-metadata.ps1) script when building API Browser metadata.
 
 ## docfx Markdown