Add magnetic top-panel corners for undersized V2.4 panels

[Eraahetor]

Which mods are added by this PR?

Adds Magnetic Top Panel - Small Panel Variant, a derivative of Printopal's Magnetic top panel for undersized 3 mm Voron 2.4 top panels.

The frame magnet is centered between the four extrusion locating features, while the panel-side part becomes a top cap with the magnet positioned outside the panel footprint. The tested version uses 10 x 3 mm magnets and includes printable STLs, STEP files, parametric OpenSCAD sources, metadata, and installation photos.

How was it tested?

Printed in ABS and physically installed on a Voron 2.4 with:

• 434 x 434 x 3 mm polycarbonate top panel
• 441 x 441 mm upward-extrusion center spacing
• 10 x 3 mm neodymium magnets
• 10.1 mm magnet pockets

Fit, magnetic alignment, and panel removal were tested successfully.

Any background context you want to provide?

The original lower-mounted carrier used too much of the limited gap around an undersized panel. Moving the magnetic interface outside the sheet and capturing the panel from above solved the clearance issue while keeping the top removable.

Screenshots (if appropriate)

Three installed-view photos are included in the mod's Images folder and embedded in its README.

Checklist

• I have read the rules available here and my mod adheres to these rules.
• This mod was created by myself and I agree to publish it under the repository license