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 touch on wall height resolution, opening placement, and room/level bounds; behavior is consistent via shared t-aware resolvers but regressions on flat walls or opening tools are possible.

Overview
Adds 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 & rendering: resolveWallTop / effective height now take an optional param t along the wall chord; the extruder tilts top vertices via applyWallEndHeightSlope. Room auto-ceiling and level max height consider both ends of sloped boundaries.

Spatial & sync: Wall-on-wall placement uses the minimum effective height across the opening’s along-wall span; the spatial manager resolves wall data from the scene and invalidates when height, offset, or support fields change.

Editor UX: Measurement guides, move handles, elevation guides, and wall-top snap highlights sample height at the correct t instead of a single constant.

Openings: Doors and windows clamp and resize against position-dependent ceiling height (readHostWallCeiling / readHostWallCeilingMaxWidth); placement and commit require fits so openings cannot poke through a sloped top unless Alt force-place.

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