feat(wall): add endHeightOffset for sloped top edge

[vducasse]

What does this PR do?

Adds an endHeightOffset property to the WallNode schema to allow wall extremities to have different heights (e.g., for creating a knee wall following a single-pitch roof slope). This adds an "End height offset" slider to the wall properties panel and updates the geometry generation to apply the slope along the top edge of the wall.

How to test

1. Open a scene in the editor and draw a standard wall.
2. Select the wall to open the properties panel.
3. Under the dimensions/properties, look for the new End height offset slider.
4. Adjust the slider and verify that the top edge of the wall tilts smoothly between the start and end points.

Screenshots / screen recording

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

Medium Risk
Wide changes to wall height resolution, mesh generation, and door/window placement constraints; regressions could affect opening fit, trims, and spatial collision on sloped walls, but scope is modeling/editor logic rather than security or persistence.

Overview
Introduces endHeightOffset on walls so the top edge can slope from start to end (knee walls / single-pitch roofs), with an End height offset control in the wall panel.

Core behavior: resolveWallTop / effective height now accept an optional parametric t along the wall; the viewer tilts extruded wall tops and adjusts crown trim, face bands, and band splits for the taller end. Room/level height and space-detection ceilings consider both ends of sloped boundary walls.

Openings & placement: Doors and windows sample the host wall ceiling at multiple t values (span corners and center), tighten resize limits (readHostWallCeilingMaxWidth), and extend clampToWall with a fits flag that slides along the wall when the sloped ceiling would clip the opening; move/place/commit paths reject invalid fits unless Alt force-place. Opening guides and wall-item placement use the minimum height over the item’s along-wall span.

Editor & sync: Measurement guides, side handles, elevation guides, and wall-top snap highlights follow per-t heights; spatial grid sync refreshes on height/slope/support field changes and wall placement checks use sampled heights at the item’s t range.

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