feat: vertical building model — stored level heights, wall inversion, decks

[wass08]

What does this PR do?

Implements the vertical building model kernel decided in the private repo's plans/editor-vertical-building-model-research.md, plus five rounds of hands-on refinement. 24 commits, reviewable stage by stage:

Stage 1 — stored level heights + wall-top inversion. LevelNode.height becomes the only vertical truth (per-building prefix sums; six divergent level-height derivations deleted, including MCP metadata.height and the first-person copy). Default walls have no height: their top is pinned to the level plane (resolveWallTop), so slabs lift only the base and top-of-level holes are impossible by construction. wall.height survives as the explicit exception with a "Follows level / Custom height" panel control derived purely from field presence. Load migration writes exact derived heights (never preset-snapped), compacts ordinals per building anchored at zero (basements stay basements), and classifies wall tops against the plane at ε = 0.20 strict < (calibrated by a 4,000-project prod census). Level rows get a height badge + presets popover (unit-aware: 8/9/10 ft imperial).

Stage 2 — persisted support hosts. Floor-placed nodes and walls remember which slab supports them (supportSlabId, written at commit only when overlapping supports disagree); elections prefer a still-valid host and silently re-elect on loss; deletion strips references undo-safely. Item support unified onto rendered slab polygons with a per-level cache.

Stage 3 — slab placement/thickness split. elevation stays the walking surface; new thickness grows downward (solid occupies [e−t, e]); migration is byte-identical for every legacy slab; pools become explicit recessed intent keeping the drag-through-zero gesture. Ceilings mirror walls (optional height = follows the level top live, minus covering-slab intrusion) and clamp to covering-slab undersides via the first cross-level query; plane-bound wall tops clamp to those undersides too (Revit's attach-to-floor-bottom, automatic). Wall-face adoption is gated to grounded slabs so decks keep their drawn polygon. Adaptive vertical editing: panel = placement; viewport drag stretches to 0.4 m then unsticks into a thin deck.

Stage 4 — decks as product surface. Stairs attach to decks (deckSlabId: rise follows the deck live, flights re-converge via a write-sync, flush landing accounting for the stair's own elected base, cutout auto-disabled). Fences host on decks and walls/fences draw on them (pointer-decided placement surface — the same ray-derived cap that fixed under-deck and stacked-slab placement). The one-gesture mezzanine/balcony tools were built, then removed in favor of catalog presets (code preserved at e30042d); the kernel they validated stays. A compact multi-selection panel ("N selected" + kind breakdown + Duplicate/Delete) with a multiSelectionFooter host slot supports the community app's save-selection-as-room flow.

Also fixes latent bugs surfaced along the way: double stair per validation click (node-click + native grid:click double dispatch), the dead mode:'build'+tool:null selection lock (stair + column tools), and the grid-plane feedback loops behind placement flicker.

How to test

1. bun dev, open a scene with a multi-level building — it loads through the migration: level rows show real stored heights (a legacy default storey reads 2.55 m), no holes at the top of any level.
2. Click a level's height badge → set 3.0 m: everything above moves, walls fill to the new plane, stairs re-converge, ceilings follow — no manual fixes.
3. Select a wall → Top: "Follows level" ↔ "Custom height"; drag its top arrow (converts to custom); slab edits under it shorten it, never raise it.
4. Draw a slab, drag its top arrow: it stretches (step feel) until ~0.4 m, then pops thin and floats as a deck. Draw walls and fences on the deck top; place items under and on it (pointer decides the surface — no flicker, no hopping between stacked slabs).
5. Add a stair, set its To destination to the deck: rise follows the deck (move the deck, the stair tracks flush), cutout controls hide.
6. On an upper level, give a slab elevation 0 + thickness 0.5: the walls and ceiling below shorten to its underside instead of clipping.
7. Multi-select the deck + stair + fences: the compact "N selected" panel docks right with Duplicate/Delete (the community app injects "Save to my catalog" below).
8. bun test — full suite; migration/census/clamp/election behaviors are unit-covered (≈250 files).

Screenshots / screen recording

N/A here — verified against real scenes via headless capture during development; happy to attach a clip on request. The lab explainer at the community app's /lab/vertical-building-model visualizes the model this implements.

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

🤖 Generated with Claude Code

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Note

High Risk
Large changes to vertical placement, wall/slab/ceiling height resolution, and scene sync affect core editor behavior and persisted node fields across many types; regressions could show as wrong elevations, clipping, or stale geometry until dirty paths run.

Overview
Adds pointer-decided slab support so placement and drag use a ray-derived walking surface (getPointedSupportSurface) and an optional maxElevation cap, fixing stacked deck/floor flicker and election at stable plan XZ instead of event-plane hits.

Introduces supportSlabId commit/read paths for floor-placed nodes, walls, and fences (resolveSupportSlabPatch, resolveWallSupportSlabPatch, resolveFenceSupportSlabPatch), plus GROUND_SUPPORT_ID when a capped commit chooses level base under an overlapping deck. Item/wall support now uses rendered slab polygons with a per-level cache invalidated on slab/wall changes.

Floating decks keep their drawn footprint (no wall-band adoption); grounded/recessed room floors still seam and adopt. Spatial-grid sync marks dependents when level height, covering slabs above/below, deck elevation, or wall geometry changes.

Auto ceilings are created height-less (follow level top); manual ceilings clamp down under covering-slab undersides from the level above, with reactive re-clamp in space-detection sync. Schema adds thickness / recessed on slabs, optional LevelNode.height and StairNode.deckSlabId, and documents supportSlabId across floor-placed kinds. Wall/slab overlap logic moves to systems/slab/slab-support with electedSlabId and pointer caps on wall election.

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Cursor Bugbot has reviewed your changes using high effort and found 2 potential issues.

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Walls miss ground host under decks

High Severity

resolveWallSupportSlabPatch doesn't persist GROUND_SUPPORT_ID when a pointer-capped election targets the ground beneath an overlapping deck. This causes walls to incorrectly lift onto the deck in subsequent uncapped elections. Note that computeWallSlabSupport also lacks a read path for GROUND_SUPPORT_ID.

 

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