Table Arrow Navigation

Goal

Make plain ArrowUp / ArrowDown table navigation stable.

• Remove the transient caret flash when moving across cells.
• Keep caret movement inside the current cell until it reaches the visual first or last line.

Plan

• [completed] Trace plain table arrow handling through the shared moveLine path.
• [completed] Add regression coverage for synchronous cross-cell movement.
• [completed] Add coverage for multi-block, soft-break, and soft-wrap cell cases.
• [completed] Route collapsed table ArrowUp / ArrowDown through table-owned moveLine.
• [completed] Add a visual-line guard before cross-cell movement.
• [completed] Run focused tests, package build, typecheck, and lint.
• [completed] Evaluate reusable knowledge and record it in solutions/.

Findings

• Plain ArrowUp / ArrowDown goes through the shared moveLine seam before browser default caret movement.
• Table navigation needs to take ownership at that seam. Repairing selection later is too late and causes visible caret flash.
• Same-cell adjacent block detection is enough for real multi-block cells.
• Wrapped single-block cells need DOM geometry, not just Slate path checks.
• editor.api.toDOMRange(...) plus caret/block rect comparison is enough to detect whether the caret is already on the visual first or last line.
• Missing DOM rects should fail conservatively and preserve previous non-throwing behavior.

Progress

• Investigated SlateReactExtensionPlugin -> withApplyTable -> overrideSelectionFromCell -> moveSelectionFromCell.
• Added a withTable.moveLine override so table owns collapsed ArrowUp / ArrowDown movement before browser default caret motion.
• Refined that override so cross-cell movement only happens once the caret reaches the visual edge of the current cell.
• Added regression coverage for:
  • synchronous plain-arrow cell movement
  • multi-block cells
  • soft-break cells
  • soft-wrapped single-block cells

Verification

• bun test packages/table/src/lib/transforms/tableSelectionAndSizing.spec.tsx packages/table/src/lib/withApplyTable.spec.ts packages/table/src/lib/transforms/overrideSelectionFromCell.spec.tsx packages/table/src/lib/transforms/moveSelectionFromCell.spec.tsx
• bun test packages/table/src/lib/withTable.spec.tsx
• pnpm install failed in prepare because bun x skiller@latest apply blocks on legacy Claude plugin migration.
• pnpm install --ignore-scripts
• pnpm turbo build --filter=./packages/table
• pnpm turbo typecheck --filter=./packages/table
• pnpm lint:fix