docs(docs): document usage and commit scopes

README.md

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+# Docker Sandbox Build
+
+This repository contains the non-Git `build-sbx.sh` utility used to create and
+configure Docker sandboxes. The script is intentionally interactive so that
+the sandbox name, mounted workspaces, copied data, API key, and cleanup actions
+are explicit.
+
+## Requirements
+
+- Bash
+- `sbx`
+- `jq`
+- `fzf` when copying an existing sandbox
+
+Run the utility from a shell with access to the `sbx` command:
+
+```bash
+./build-sbx.sh
+```
+
+## Commit Conventions
+
+This project uses [Conventional Commits](https://www.conventionalcommits.org/).
+The project is below version 1.0.0, so changes must not intentionally introduce
+breaking behavior. Every commit uses a type and a scope.
+
+Supported types:
+
+- `feat`: adds or extends behavior
+- `fix`: corrects behavior
+- `docs`: changes documentation
+- `style`: changes formatting without changing behavior
+- `refactor`: changes implementation without changing behavior
+
+Established scopes:
+
+- `kit`: sandbox kit, image template, creation, and configuration
+- `workspace`: workspace selection, naming, and cleanup workflow
+- `docs`: README and project documentation
+
+Examples:
+
+```text
+feat(kit): create configured sandbox image
+docs(docs): document commit conventions
+```