hoist EMPTY_SET default in MemoriesGrid

[ved015]

Summary

Hoisted the new Set() default parameter in MemoriesGrid to a module-level constant named EMPTY_SET.

Details

The selectedDocumentIds = new Set() default parameter was causing a performance bottleneck. Because a new Set was being instantiated on every render cycle, its reference was never stable. This invalidated the React.memo optimization on the DocumentCard components, forcing every visible card to re-render whenever the parent MemoriesGrid updated.

Use

• Component Efficiency: Restores the effectiveness of memo() for the masonry item rendering.
• Render Cost: Prevents cascading re-renders of 100+ cards during common actions like opening the chat sidebar or space navigation.

@Dhravya please have a look

[ved015]

@MaheshtheDev this can be merged

[MaheshtheDev]

LGTM