feat(xlsx): inline hyperlinks in data rows (#325)

[productdevbook]

Closes #325.

Problem

writeXlsx's columns + data API only accepted scalar CellValue for row values. Hyperlinks with separate display text could only be expressed via the parallel cells: Map<"row,col", …> API — meaning three sources of truth for one logical "Link" column (schema in columns, value in cells, coordinate in a hand-computed "row,col" string). Reordering or inserting columns broke the index math.

Solution

Allow rich values inline in data rows — an ExcelJS-compatible { text, hyperlink, tooltip? } shape, keyed by the column's key. The cells map path is fully preserved for backward compatibility.

import { writeXlsx, link } from "hucre/xlsx"

await writeXlsx({
  sheets: [{
    name: "Summary",
    columns: [{ header: "Link", key: "link" }, { header: "ID", key: "id" }],
    data: [
      { link: link("Open", "https://example.com/items/abc-123"), id: "abc-123" },
      { link: { text: "Open", hyperlink: "https://example.com/items/def-456" }, id: "def-456" },
    ],
  }],
})

Changes

• HyperlinkValue type + widened data type. CellValue union is left untouched, so CSV/ODS/formula serialization paths are unaffected.
• link(text, hyperlink, tooltip?) helper exported from both hucre and hucre/xlsx. A plain object is also accepted (stays JSON-serializable).
• #-prefixed targets become internal references (location), e.g. "#Sheet2!A1".
• collectHyperlinks now reads the resolved grid, so links from both inline data rows and the cells map are collected from a single source (this also closes the existing gap where a cells-map hyperlink was never carried onto the ResolvedCell).
• Non-XLSX consumers (ODS writer, pivot source rows) unwrap rich values to scalar text.

Design note

Surveyed competing libraries (ExcelJS, SheetJS, write-excel-file). { text, hyperlink, tooltip } is the most familiar shape in the ecosystem (ExcelJS) and maps almost 1:1 to hucre's internal Hyperlink type. Issue Option A (inline) was chosen as the core solution; Option B (column-level getter) was left out of scope.

Testing

• pnpm test: 7472 tests pass (including lint + typecheck).
• 6 new tests: raw object, link() helper, tooltip round-trip, #-internal ref, scalar values left untouched, mixed data + cells on the same sheet.
• README updated with an inline data + link() example.

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