Rarely set fields move into one optional boxed NodeExtras, and large NodeKind payloads (images,
live shapes, blends, envelopes) are boxed. Every object, and every undo step that copies it,
shrinks: a 50k-path move keeps ~24.5 MB per step instead of ~40 MB. Files stay byte-identical
(Node keeps its flat JSON through a borrowed Serialize and a from-wire Deserialize, no flatten),
and loading is slightly faster. Undo and redo reuse their step's size estimate instead of
walking the document again (8.3 -> 5.6 ms for a 50k-path move).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VmMmc1J8XeNLxhRihWv9cc
# Conflicts:
# crates/engine/src/cmd/graph.rs
# crates/svg/src/export.rs
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