chore: add VHS tooling for uptop TUI screenshots

Backfill tool, crop tool, demo tape, seed data, and setup script
extracted from the uptop repo for clean separation.

README.md

@@ -1,3 +1,26 @@
 # uptop-vhs
 
-VHS tape files and tooling for generating uptop TUI screenshots
+VHS tape files and tooling for generating [uptop](https://gitea.lerkolabs.com/lerko/uptop) TUI screenshots.
+
+## Contents
+
+- `demo.tape` — VHS tape that drives the TUI through each tab
+- `seed.yaml` — sample monitor/site definitions for realistic demo data
+- `setup.sh` — bootstrap script: builds uptop, seeds DB, runs backfill
+- `backfill/` — Go tool that generates realistic historical check data
+- `crop/` — Go tool that crops VHS output into per-tab screenshots
+
+## Usage
+
+```bash
+# 1. Set up and run the demo
+./setup.sh
+
+# 2. Record with VHS
+vhs demo.tape
+
+# 3. Crop into individual screenshots
+go run ./crop/
+```
+
+Screenshots land in `screenshots/` — copy them to the uptop repo's `screenshots/` directory.