Initial authoring system prototype

prototype/README.md

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+# Read-only Package Preview Prototype
+
+This is the first authoring-system vertical slice. It reads a Scrivener project, checks the project structure, and builds an on-screen package preview. It does **not** call a model and it does **not** write to Scrivener.
+
+Run from `Authoring_System`:
+
+```sh
+python3 prototype/app.py
+```
+
+Then open [http://127.0.0.1:8765](http://127.0.0.1:8765).
+
+To point it at another project:
+
+```sh
+python3 prototype/app.py --project /absolute/path/to/Book.scriv
+```
+
+The app binds scene/brief pairs by the visible `Scene X` labels for this read-only prototype. The next phase will persist UUID bindings in a sidecar, so later renaming does not break relationships.