feat: Add deck tester feature to import custom deck lists and immediately start solo games.

docs/development/devlog/2025-12-15-002500_deck_tester_feature.md

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+# Deck Tester Feature Implementation
+
+## Objective
+Create a way to add a cards list to generate a deck and directly enter the game ui to test the imported deck, using the same exact game and battlefield of the draft.
+
+## Implementation Details
+
+### Frontend
+1.  **DeckTester Component (`src/client/src/modules/tester/DeckTester.tsx`)**:
+    - Created a new component that allows users to input a deck list (text area or file upload).
+    - Reused `CardParserService` and `ScryfallService` to parse the list and fetch card data.
+    - Implemented image caching logic (sending to `/api/cards/cache`).
+    - Connects to socket and emits `start_solo_test`.
+    - Upon success, switches view to `GameRoom` with the received `room` and `game` state.
+
+2.  **App Integration (`src/client/src/App.tsx`)**:
+    - Added a new "Deck Tester" tab to the main navigation.
+    - Uses the `Play` icon from lucide-react.
+
+3.  **GameRoom Enhancement (`src/client/src/modules/lobby/GameRoom.tsx`)**:
+    - Added `initialGameState` prop to allow initializing the `GameView` immediately without waiting for a socket update (handling potential race conditions or state sync delays).
+
+### Backend
+1.  **Socket Event (`src/server/index.ts`)**:
+    - Added `start_solo_test` event handler.
+    - Creates a room with status `playing`.
+    - Initializes a game instance.
+    - Adds cards from the provided deck list to the game (library zone).
+    - Emits `room_update` and `game_update` to the client.
+
+## Outcome
+The user can now navigate to "Deck Tester", paste a deck list, and immediately enter the 3D Game View to test interactions on the battlefield. This reuses the entire Draft Game infrastructure, ensuring consistency.