Complete 0.1.x hardening series. 419 tests (171 Rust + 248 TypeScript).

• Style roundtrip: gradient fills, diagonal borders, DXF styles, cell named styles
• Formula metadata: array formulas, shared formulas, formulaRef, sharedIndex
• Feature roundtrip: hyperlinks, comments, data validation, conditional formatting, sheet protection, page setup
• Edge cases: empty workbooks, malformed XML, boundary values
• Error handling: corrupted files, invalid inputs, graceful degradation
• Streaming & benchmarks: 100K row read/write, parallel parsing, buffer scaling
• Utilities: cell refs, dates, format codes, CSV/HTML/JSON conversion

• push_entity() — zero-allocation XML entity resolution
• Vec::with_capacity() on all XML parse buffers (11 sites)
• from_utf8().unwrap_or_default() replaces from_utf8_lossy() (6 sites)
• entries.remove() in StreamingReader — moves data instead of cloning
• drain() in collect_preserved() — moves preserved entries
• #[non_exhaustive] on error enum

• Module-scoped CELL_REF_RE regex (hoisted from hot loop)
• isolatedDeclarations: true in tsconfig
• Shared WASM init via __tests__/setup.ts

• Migration guide: SheetJS
• Migration guide: ExcelJS
• Usage examples cookbook
• Release roadmap

• GitHub Actions pinned to stable versions
• Rust toolchain: @stable
• Node.js engine: >=24.0.0

First public release.

• Full XLSX read/write with Rust WASM core
• Cell styling — fonts, fills, borders, alignment, number formats via StyleBuilder
• Data validation — list, number, date, text length, custom formula
• Conditional formatting — color scales, data bars, icon sets, formula-based rules
• Frozen panes, hyperlinks, comments, sheet protection, page setup
• Rich text with RichTextBuilder
• Named ranges, document properties, workbook views, calc chain
• Streaming reader/writer for large files
• Parallel sheet parsing (rayon)
• Cell reference utilities, date utilities, format utilities
• Sheet conversion utilities (JSON, CSV, HTML, array-of-arrays)
• Browser Blob download support
• 342 tests (170 Rust + 172 TypeScript)