P5m made the model accept blocks in cells, but the atomic-insert path
(`insertAtomicBlock`) only special-cased columns — with the caret in a cell it
fell through to the top-level split, dropping the block NEXT TO the table
instead of inside the cell. So "blocks in cells" was model-only, not reachable.
Adds an `insertIntoCell` branch mirroring `insertIntoColumn`, one level deeper
(container path [tableIdx, rowIdx, cellIdx, blockInCell, ...]): empty-cell
paragraph → replace in place (+ trailing paragraph); non-empty → split the
cell's block around the inserted one. So insert-callout / divider / image (and
any atomic insert) with the caret in a cell now land inside that cell.
New test `insert-block-types.test.ts` (3/3): inserts into the cell (single
top-level table preserved), callout lands inside, non-empty cell splits
(para("a") · divider · para("b")). npm run check: 0 new errors.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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