* security: linear vector import, stroking and rounding, validation and a cycle check for dev snapshots
Closing a subpath, rounding corners and chaining stroke runs each rescanned the whole
network per step, and Document::validate searched a parent's children per child. They now
update only the current subpath's last segment, rebuild each region loop in one pass, walk
per-vertex adjacency lists, and check edges against a once-built index. A dev snapshot whose
layers contain a cycle under the root is refused instead of reconstructed.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
* fix(doc): address review findings for snapshot children and 2-segment rounded loops
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Co-authored-by: Claude Sonnet 5.5 <noreply@anthropic.com>