Refactor to PSR-4: rename files and switch namespace

- Rename files to PascalCase: Product_Type → ProductType, Cart_Handler →
  CartHandler, Product_Selector → ProductSelector, Stock_Manager →
  StockManager, Admin/Product_Data → Admin/ProductData
- Switch namespace from WC_Composable_Product to Magdev\WcComposableProduct
- Update all cross-references in PHP, CSS, JS, translations, and docs

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -36,13 +36,13 @@ wc-composable-product/
 ├── cache/                     # Twig template cache (writable, gitignored)
 ├── includes/
 │   ├── Admin/
-│   │   ├── Product_Data.php   # Product data tab & meta boxes
+│   │   ├── ProductData.php    # Product data tab & meta boxes
 │   │   └── Settings.php       # WooCommerce settings integration
-│   ├── Cart_Handler.php       # Add-to-cart & cart display logic (with stock validation)
+│   ├── CartHandler.php        # Add-to-cart & cart display logic (with stock validation)
 │   ├── Plugin.php             # Main plugin class (Singleton)
-│   ├── Product_Selector.php   # Frontend product selector renderer (with stock info)
-│   ├── Product_Type.php       # Custom WC_Product extension
-│   └── Stock_Manager.php      # Stock management & inventory tracking
+│   ├── ProductSelector.php    # Frontend product selector renderer (with stock info)
+│   ├── ProductType.php        # Custom WC_Product extension
+│   └── StockManager.php       # Stock management & inventory tracking
 ├── languages/                 # Translation files (.pot, .po, .mo)
 ├── releases/                  # Release packages (gitignored)
 ├── templates/
@@ -61,29 +61,29 @@ wc-composable-product/
    - Registers hooks, manages asset enqueuing, provides template rendering API
    - Settings.php is lazy-loaded via `woocommerce_get_settings_pages` filter (not in `includes()`) to avoid "Class WC_Settings_Page not found" errors
 
-2. **Product_Type.php** — Custom WooCommerce product type (`composable`)
+2. **ProductType.php** — Custom WooCommerce product type (`composable`)
    - Extends `WC_Product`
    - Queries available products via `get_available_products()` using `WP_Query`
    - **Critical**: Uses `tax_query` with `product_type` taxonomy to exclude composable products (NOT `meta_query` — WooCommerce stores product types as taxonomy terms)
    - Handles variable products by expanding them into individual variations via `get_children()`
    - Products are filtered by `is_purchasable()` only (not `is_in_stock()` — stock is shown visually and validated at add-to-cart)
 
-3. **Cart_Handler.php** — Cart integration
+3. **CartHandler.php** — Cart integration
    - Validates selections, stores selected products in cart meta, calculates pricing
    - Uses `woocommerce_is_purchasable` filter to hide default add-to-cart button for composable products
    - Price recalculation uses a static `$already_calculated` flag per request (no persistent session flags — `set_price()` is in-memory only)
 
-4. **Product_Selector.php** — Frontend renderer
+4. **ProductSelector.php** — Frontend renderer
    - Renders Twig template with product data, stock info, and pre-formatted price HTML via `wc_price()`
 
-5. **Admin/Product_Data.php** — Product edit interface
+5. **Admin/ProductData.php** — Product edit interface
    - Adds "Composable Options" tab with category/tag/SKU selection fields
    - Saved meta: `_composable_selection_limit`, `_composable_pricing_mode`, `_composable_criteria_type`, `_composable_categories`, `_composable_tags`, `_composable_skus`
 
 6. **Admin/Settings.php** — Global settings (extends `WC_Settings_Page`)
    - Default selection limit, pricing mode, display preferences
 
-7. **Stock_Manager.php** — Inventory management
+7. **StockManager.php** — Inventory management
    - Stock validation, automatic deduction on order completion, restoration on cancellation
    - Prevents WooCommerce double-deduction via `woocommerce_can_reduce_order_stock`
 
@@ -91,11 +91,11 @@ wc-composable-product/
 
 **Product Creation:** Admin selects "Composable product" type → configures criteria/limits/pricing → metadata saved as `_composable_*` fields
 
-**Frontend Display:** `Cart_Handler::render_product_selector()` → `Product_Type::get_available_products()` queries products via taxonomy/SKU → `Product_Selector::render()` passes data to Twig template → JavaScript handles selection UI
+**Frontend Display:** `CartHandler::render_product_selector()` → `ProductType::get_available_products()` queries products via taxonomy/SKU → `ProductSelector::render()` passes data to Twig template → JavaScript handles selection UI
 
 **Add to Cart:** Customer selects products → JS validates limit → AJAX request with `composable_products[]` → server-side validation (selection + stock) → selections stored in cart item data → price calculated per pricing mode
 
-**Order Processing:** Order completed → `Stock_Manager` deducts inventory → order notes added for audit → on cancellation/refund: stock restored
+**Order Processing:** Order completed → `StockManager` deducts inventory → order notes added for audit → on cancellation/refund: stock restored
 
 ### Key Hooks