feat: add bmad-eval-runner skill with isolation, dependency staging, and full docs

docs/_diagrams/README.md

@@ -0,0 +1,36 @@
+# Diagram Sources
+
+Excalidraw source files for diagrams embedded in the docs. Edit the `.excalidraw` source here, then export PNG to `website/public/img/`.
+
+## Files
+
+| Source                          | Rendered PNG                                        | Used In                                      |
+| ------------------------------- | --------------------------------------------------- | -------------------------------------------- |
+| `eval-test-types.excalidraw`    | `website/public/img/eval-test-types.png`            | explanation/what-are-evals.md                |
+
+## Exporting to PNG
+
+A headless renderer is included. From the project root:
+
+```bash
+# Install playwright once if you have not (~50 MB)
+npm install --no-save playwright
+
+# Render any source file in this folder
+node docs/_diagrams/render.mjs \
+  docs/_diagrams/eval-test-types.excalidraw \
+  website/public/img/eval-test-types.png \
+  2
+```
+
+The third arg is the scale factor (2 = retina). The renderer loads `@excalidraw/utils` from esm.sh, exports to canvas, and writes the PNG. Internet is required on the first run; thereafter esm.sh caches.
+
+If you prefer the GUI, drag the `.excalidraw` onto [excalidraw.com](https://excalidraw.com) and use File > Export image > PNG (scale 2x, white background).
+
+The PNG is committed alongside the source so the docs render without a build step.
+
+## Convention
+
+- Two-character element indices only (`a0`, `aZ`, `b3`). Three-char indices like `d9a` silently break the file.
+- Use distinct fill colors per logical group (e.g., workspace, artifact flow, trigger flow, output).
+- Keep diagrams legible at 1200px wide.