The previous commit let model-block hatches into the shared
`hatch_models_arc` so paper-layout content viewports could pick them
up through their GPU pipeline. PaperCanvas was reading the same arc
and projecting every entry through the paper camera, so model hatches
got a second copy on the paper sheet — at huge / off-position
coordinates because their `world_origin` is in offset-subtracted
local space, not paper millimetres.
Split the canvas-side accessors:
- `paper_canvas_hatches` now iterates `self.hatches` directly (the
source map is keyed by entity handle) and keeps only entries whose
owner is the active paper-layout block. The flattened arc only
carries pattern names, so handle-based filtering had to move here.
- `paper_canvas_wipeouts` iterates entities likewise; paper-block
wipeouts get `[0;3]` `world_offset` so the boundary is in paper
millimetres.
GPU paths still call `hatch_models_arc` / `wipeout_models_arc` which
return everything — the per-viewport scissor / camera projection
silently culls the wrong-block hatches there.
e9e3bbbca1