US09-05: Automate Documentation Acceptance

docs/index.md

@@ -42,6 +42,25 @@ what it changes on disk or on the server, and what it refuses.
 - [Recovery](recovery.md) — what the application resolves by itself, and what needs
   you.
 
+## Keeping these pages true
+
+Documentation that disagrees with the application is worse than none, because it is
+trusted. So one command compares them:
+
+```bash
+python -m photo_pipeline docs-gate
+```
+
+It runs every `phase_i` check — dead links and anchors, pages nobody links to, images
+nobody shows, settings, commands, exit codes, error codes, and states that no longer
+exist in the code, the pages rendering in a real browser without a console or policy
+error, and the screenshots still showing what the application shows. It retains its
+evidence and **accepts no skipped check**: a check that did not run is a page nobody
+compared. CI runs it on every pull request.
+
+The repository's own build, test, and release notes live in the
+[README](../README.md).
+
 ## Conventions
 
 A page tells you what a stage **changes on disk or on the server** before it tells