The SpeedyNote-style page binding the user asked for: a notebook is an ordered
list of logical pages, each a SOURCE page (renders PDF page N, vector preserved)
or a BLANK inserted page. Crucially, inserting/reordering logical pages does NOT
renumber the PDF underlay — each page carries its source index. Copy-on-write
edits (insertBlankAt/After, removeAt, move) return a new immutable PageMap;
out-of-range edits throw RangeError; value equality + unmodifiable page list.
Pure model (no DB/widget) so it's fully unit-tested; the notebook_pages table +
viewport wire it later.
flutter analyze lib/editor clean; 156/156 tests (+11).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
