Editable Whiteboard and Operation Log

Copyright 2026 Sahil Kadadekar
SPDX-License-Identifier: Apache-2.0

The immutable add/update/delete operations, field-level inverse operations,
shape contract, and rectangle/ellipse/segment hit-testing are adapted from
the author's Apache-2.0-licensed whiteboard client (2026).
The original copyright and license are preserved in LICENSE.txt.

Modifications for this browser adaptation:
- Explicit insertion positions preserve z-order when undoing deletion.
- Strict runtime validation and atomic command batches.
- Replayable, versioned JSON history and single-tab browser persistence.
- Gesture previews, bounded geometry and device-pixel-ratio rendering.
- Pointer input in whole board units.
- Fresh synthetic workflow fixture and a new project-local interface/article.

No original account, board or server fixture is included.
This adaptation does not include the original network collaboration service.