editor: FIX - door and window placement works in 2D-only view

[ivnnv]

What does this PR do?

In 2D-only view the hidden 3D pane had display: none, so its canvas had no size and the scene never mounted, and with it the door and window tools. The 2D plan sends its wall:* events to those tools, so placing a door or window in 2D-only view just showed the cursor chip and the click placed nothing, until 3D was opened at least once. The hidden pane now keeps its size (visibility: hidden, no pointer events, render still paused), so the tools are there from the first hover.

Side effect worth knowing: since the 3D camera now mounts in 2D-only view too, the plan opens aligned to the camera like it already did after visiting 3D once.

How to test

1. Reload a project with walls straight into 2D-only view (dont open 3D or Split)
2. Pick Door and hover a wall: the door draws on the wall with its gap and swing
3. Click: the door is placed where it was drawn. Same for Window

Screenshots / screen recording

Before (fresh 2D-only load, Door on a wall, only the chip):

After:

Checklist

• I've tested this locally with bun dev
• My code follows the existing code style (run bun check to verify)
• I've updated relevant documentation (if applicable)
• This PR targets the main branch

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Note

Low Risk
Localized layout/CSS change in the editor viewer grid with clear accessibility handling; main tradeoff is slightly more 3D initialization work in 2D-only view while render stays paused.

Overview
Fixes door and window placement in 2D-only view by changing how the always-mounted 3D viewer is hidden when no 3D pane is active.

Instead of display: none (which collapsed the canvas to zero size and prevented the scene and ToolManager from mounting), the hidden 3D pane now uses visibility: hidden with pointer-events: none while still occupying the grid cell, so WebGL context is preserved and placement tools are available for 2D wall:* events from the first load. aria-hidden is set when the 3D pane is not shown.

Side effect: the 3D camera now initializes in 2D-only mode too, so the floor plan opens aligned to the camera without needing to open 3D first. Rendering remains paused via existing renderPaused={!show3d && !showLoader}.

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