Comment threads open by default, visual overwrite previews, and per-cell citations

Features

PDF comment threads now open automatically. When you open a document with comment annotations, each thread expands below its marker without any extra click. You can still collapse or expand individual threads by clicking the yellow comment icon.
Visual overwrite preview in approval cards. When a workbook write would replace existing data, the approval card now shows a color-coded cell grid — occupied cells are highlighted in red, empty cells are muted — so you can see exactly what will be overwritten before approving. Individual cells are clickable to navigate directly to them.
Per-cell citations for data tables in the Excel add-in. When CoAudit populates a table of numbers, each cell can now carry its own evidence. The value and its source quote are written together in a single approved operation, without requiring a separate citation step per cell.

"Replace existing data" button now shows the correct cell count. The button previously reported the number of operations (e.g., "1 area") rather than the number of cells actually at risk. It now shows the true count — for example, a range with 129 occupied cells reads "129 cells."
Clearing only evidence from a cell no longer looks like a data casualty. When a workbook change removes only a citation or rationale — not the cell value itself — the approval preview no longer incorrectly lists the existing cell value as something being deleted.
Manual approval mode now always asks before writing. Previously, writes confirmed to target empty cells would sometimes skip the approval step even in Manual mode. Approval is now correctly requested in all cases; the auto-skip behavior is limited to Skip mode and active write sessions.
Workbook reads that fail no longer silently allow writes to proceed. If the live cell read before an overwrite approval cannot complete, an amber note now appears with a "Try again" link. No write is approved until the current cell contents have been confirmed.
Math calculator operand values no longer obscured by a tooltip. A tooltip on the calculator's drag handle was overlapping the numbers displayed in each row. The tooltip has been removed; drag-to-reorder and keyboard reordering still work as before.