Floorplan export emits a blank page for the dedicated roof support level #618

Summary

resolveExportLevels() in packages/editor/src/lib/floorplan/floorplan-export.tsx
collects every level child of the active building:

levelNodes = childIds.map((id) => nodes[id]).filter((n): n is AnyNode => n?.type === 'level')

A dedicated roof support level (metadata.role === 'roof') is included, so the
exported PDF gains a page titled with the roof level's label that contains only
the roof outline — no rooms, no dimensions, nothing a floor plan is for.

The project's own agent guide states the intent explicitly: "A dedicated roof
support level is valid and should not count as an occupied story." The
elevation math (getLevelElevations) and the level UI honour that; the plan
export does not.

Reproduce

1. Build a house, add a roof via the roof tool (it creates a Roof level with
   metadata.role = 'roof').
2. Settings → export the floor plan.
3. The PDF has an extra page for the roof level.

Suggested fix

levelNodes = childIds
  .map((id) => nodes[id])
  .filter((n): n is AnyNode => n?.type === 'level')
  .filter((n) => (n.metadata as { role?: unknown } | undefined)?.role !== 'roof')

A roof-plan drawing type already exists in DRAWING_TYPE_OPTIONS, so a roof
level could later get a page of its own deliberately — but not as a blank
floor plan.

Version

@pascal-app/editor@1.0.0-beta.4