Add AGENTS.md to the repository (#28651)

Author: FaithOmbongi

AGENTS.md

@@ -0,0 +1,42 @@
+# Agent Quick Guide
+
+Top-level entrypoint for agents working in this repository.
+
+## Authority
+
+If this file and `.github/copilot-instructions.md` ever differ, follow:
+
+1. `.github/copilot-instructions.md`
+2. The prompt and template files it routes you to
+
+This file is intentionally thin to avoid split-brain guidance.
+
+## Read first
+
+Before doing docs work in this repo:
+
+1. Read `.github/copilot-instructions.md`
+2. Determine whether the task is **authoring/updating** or **review**
+3. Load the prompt file that `.github/copilot-instructions.md` tells you to read first
+
+## Repo map
+
+- `api-reference/*/api/` — API operation topics
+- `api-reference/*/resources/` — resource and enum topics
+- `changelog/` — API change records
+- `concepts/whats-new-overview.md` — monthly release highlights
+- `concepts/` — conceptual topics such as tutorials, conceptual overviews, guides
+- `api-reference/*/toc/toc.mapping.json` — API reference TOC mapping
+- `api-reference/*/includes/rbac-for-apis/` — RBAC include files
+- `temp-docstubs/` — temporary authoring inputs
+
+## Workflow
+
+1. Start with `.github/copilot-instructions.md`
+2. Load the correct scenario guidance
+3. Make scoped changes only
+4. Run the validation expected by the loaded workflow
+
+## Rule of thumb
+
+Do not duplicate detailed rules in this file. Keep detailed authoring, review, changelog, What's New, TOC, enum, and RBAC guidance in the files referenced by `.github/copilot-instructions.md`.