fix(preview): bound row and sheet indices before ExcelJS, reuse merges per tile, cap format decimals

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ExcelJS stores a row at _rows[r - 1] and a sheet at _worksheets[sheetId], and
walks or slices those arrays up to the largest index, so the index a row or
sheet claims is a cost of its own. Admission now reads each <row> tag's
attributes in order and refuses an r outside 1-1048576 (absent r is fine), and
a counter for the resolved xl/workbook.xml reads every <sheet> tag and refuses
one that does not parse or whose sheetId is not plain digits up to
LIMITS.maxSheetId (65535).

sendTile no longer reads sheet.model, which rebuilt every row and cell model on
each tile: the merges read in worksheetMetadata are kept in mergesById next to
populatedRowsById, replaced on load and cleared on dispose.

Number formats cap decimals at 30, as Excel does; toLocaleString throws a
RangeError above 100 and the whole grid was replaced by the error.

Docs: CLAUDE.md and architecture-invariants describe both bounds and the merge
reuse. SPREADSHEET_ASSET_VERSION is recomputed for the edited worker and core.

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This commit is contained in:

Aamer Akhter

2026-10-03 12:33:35 -04:00

parent 2d0ffb71aa

commit c1811fd716

7 changed files with 153 additions and 9 deletions

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docs/architecture-invariants.md

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