feat: limit Cube Manager sidebar to 400px max-width on large screens and update documentation.

docs/development/CENTRAL.md

@@ -65,3 +65,4 @@
 - [Squared Art Crops](./devlog/2025-12-17-030500_squared_art_crops.md): Completed. Enforced square aspect ratio for art-crop thumbnails to optimize visual density and stacking.
 - [Fix Expansion Generation Limit](./devlog/2025-12-17-024500_fix_expansion_generation_limit.md): Completed. Implemented "Unlimited Pool" mode for expansion drafts to allow generating large numbers of packs from singleton set data.
 - [Change Default Filter Flags](./devlog/2025-12-17-025500_change_default_flags.md): Completed. Updated client and server defaults for "Ignore Basic Lands", "Ignore Commander Sets", and "Ignore Tokens" to be unchecked (false).
+- [Sidebar Max Width](./devlog/2025-12-17-031000_sidebar_max_width.md): Completed. Constrained the left sidebar in Cube Manager to a maximum width of 400px on large screens to improve layout balance.

docs/development/devlog/2025-12-17-031000_sidebar_max_width.md

@@ -0,0 +1,14 @@
+
+# 2025-12-17 Left Sidebar Max Width
+
+## Objective
+Limit the left sidebar in the Cube Manager to a maximum width of 400px on large screens to prevent it from becoming excessively wide on high-resolution displays.
+
+## Changes
+1.  **Layout Refactor (`src/client/src/modules/cube/CubeManager.tsx`)**:
+    *   Change the main container from a CSS Grid (`grid-cols-12`) to a Flexbox layout (`flex-col lg:flex-row`).
+    *   Set the left column width to `lg:w-1/3` with a strict `lg:max-w-[400px]` constraint.
+    *   Set the right column to `flex-1` to take up remaining space.
+
+## Rationale
+The previous `lg:col-span-4` (33% width) scaled indefinitely on large screens (e.g., 2560px wide -> ~850px sidebar), which wastes space and stretches control inputs. A max-width constraint ensures the controls remain compact while the main content area (packs display) benefits from the extra screen real estate.