docs: add CLAUDE.md project instructions

Co-Authored-By: Virgil <virgil@lethean.io>

CLAUDE.md

@@ -0,0 +1,49 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Overview
+
+This is `lthn/php-plug-storage`, a Composer library providing storage provider integrations for the Plug framework. It depends on `lthn/php` (the core framework) and wraps Bunny CDN's storage API behind a driver-based abstraction.
+
+## Commands
+
+```bash
+composer install          # Install dependencies
+```
+
+There are no tests, linting, or build steps in this package.
+
+## Architecture
+
+**Namespace:** `Core\Plug\Storage\` (PSR-4 autoloaded from `src/`)
+
+### Contract Layer (`src/Contract/`)
+
+Four interfaces define storage operations. All return `Core\Plug\Response` (from the core framework):
+
+- `Uploadable` — file and content uploads
+- `Downloadable` — content retrieval and file downloads
+- `Deletable` — single and bulk file deletion
+- `Browseable` — directory listing, existence checks, file size
+
+### Bunny Implementation (`src/Bunny/`)
+
+Each contract has a corresponding Bunny CDN implementation (`Upload`, `Download`, `Delete`, `Browse`). They share a common pattern:
+- Constructor accepts optional credentials or reads from config (`cdn.bunny.{zone}.api_key`, `cdn.bunny.{zone}.storage_zone`, `cdn.bunny.{zone}.region`)
+- Lazy-initialized `Bunny\Storage\Client`
+- `isConfigured()` guard before operations
+- `BuildsResponse` trait for consistent `ok()`/`error()` responses
+- Static `public()`/`private()` factory methods for zone selection
+
+**VBucket** (`src/Bunny/VBucket.php`) provides workspace-isolated storage. It hashes a domain via `Core\Crypt\LthnHash::vBucketId()` and prefixes all paths with the resulting ID. It combines upload, download, delete, list, and exists operations in one class rather than implementing the individual contracts.
+
+### StorageManager (`src/StorageManager.php`)
+
+Factory that resolves operations by driver name. Configured via `cdn.storage_driver` config key (defaults to `bunny`). Supports zone switching and custom driver registration via `extend()`.
+
+## Key Patterns
+
+- All storage operations return `Core\Plug\Response`, never throw — errors are wrapped via `BuildsResponse::error()`.
+- Zone (`public`/`private`) is threaded through constructors, not set after instantiation.
+- Adding a new storage provider means: implement the four contracts, then register via `StorageManager::extend()`.