Feature: Room categories (subspaces) with drag and drop

[mjkatgithub]

Goal

Represent subspaces as room categories and allow room reordering/moving via drag and drop.

Scope

• Display subspaces as categories in the room list
• Move rooms between categories with drag and drop
• Persist ordering using Matrix m.space.child and order

Acceptance Criteria

• Categories are rendered correctly from subspaces
• Rooms can be moved between categories
• Ordering and assignment remain stable after reload

Test Checklist

Unit

• Category mapping from subspaces
• Ordering calculation and serialization

Integration

• Drag and drop updates the UI immediately
• Persisted category assignment/order is restored correctly

E2E

• Move a room to another category and verify placement
• Reload and verify assignment/order persistence

branch

feature/room-category-dnd