chore: add launch Claude Code skill

.claude/skills/launch/SKILL.md

@@ -0,0 +1,43 @@
+---
+name: launch
+description: Use this skill when asked to run, start, dev-serve, or preview ui, or to confirm a change works in the real app. Covers the tsup watch build for packages/ui paired with the apps/playground Vite app used to exercise exported components.
+---
+
+# Launch ui
+
+Turborepo internal-packages repo with no runnable frontend of its own — `packages/ui`
+is a component library, not an app. The one genuine "launch" target is
+`apps/playground`, a small Vite app that imports `@behindthemusictree/ui` and is used
+to manually exercise exported components. `pnpm dev` at the repo root runs `packages/ui`'s
+`tsup --watch` build in parallel with the playground's Vite dev server via Turborepo.
+
+## 1. Install
+
+```bash
+pnpm install
+```
+
+## 2. Start the dev environment
+
+```bash
+pnpm dev
+```
+
+This is `turbo run dev`, which (per `turbo.json`, `dev` is `cache: false` and
+`persistent: true`) runs both workspace `dev` scripts concurrently:
+
+- `packages/ui`: `tsup --watch` — rebuilds the library on every source change.
+- `apps/playground`: `vite` — dev server that consumes the workspace `@behindthemusictree/ui`
+  package, printing its own local URL (Vite's default is `http://localhost:5173`).
+
+## 3. Verify
+
+Open the printed playground URL. Since `apps/playground` depends on
+`@behindthemusictree/ui` as a `workspace:*` package and `tsup --watch` is rebuilding
+it live, edits to `packages/ui` source should hot-reload into the playground without
+restarting anything.
+
+Note: this package does not ship `@behindthemusictree/brand`'s `tokens/theme.css` —
+if playground styling looks off, check that the playground itself imports the design
+tokens (see `apps/playground/src`), since `packages/ui` components only reference the
+CSS custom properties, they don't define them.

CHANGELOG.md

@@ -5,6 +5,10 @@ Format based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ## [Unreleased]
 
+### Added
+
+- **Dev tooling**: Added a `launch` Claude Code skill (`.claude/skills/launch/`) documenting how to start the local dev environment.
+
 ## [0.2.0] - 2026-10-21
 
 ### Added