fix(HF-162): scale TEXT percentage formats before rounding

[Tobiadefami]

Context

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Types of changes

• Breaking change (a fix or a feature because of which an existing functionality doesn't work as expected anymore)
• New feature or improvement (a non-breaking change that adds functionality)
• Bug fix (a non-breaking change that fixes an issue)
• Additional language file, or a change to an existing language file (translations)
• Change to the documentation

Related issues:

1. Fixes #...

Checklist:

• I have reviewed the guidelines about Contributing to HyperFormula and I confirm that my code follows the code style of this project.
• I have signed the Contributor License Agreement.
• My change is compliant with the OpenDocument standard.
• My change is compatible with Microsoft Excel.
• My change is compatible with Google Sheets.
• I described my changes in the CHANGELOG.md file.
• My changes require a documentation update.
• My changes require a migration guide.

---

Note

Medium Risk
Changes default TEXT output for % formats (behavior fix aligned with Excel), which may affect spreadsheets that relied on the old scaling or manual *100 workarounds.

Overview
Fixes TEXT percentage number formats so they match Excel: each active % in the format string multiplies the numeric value by 100 before rounding, so TEXT(0.0123,"0.00%") returns 1.23% instead of 0.01%.

The number-format parser now tokenizes %, quoted literals, and escapes separately (quoted or escaped % stay literal and do not scale). numberFormat applies scaling once per percent token, surfaces #VALUE! if scaling overflows, and appends % in the output. CHANGELOG and the Excel compatibility guide document the behavior and note that workarounds that manually multiply by 100 can be removed.

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[cla-external-contractor-signup]

@Tobiadefami thanks for the pull request. No CLA step needed here — our records show you signed the Contributor License Agreement on 2026-07-31. That signature came from our previous signing form and has been carried over, so there is nothing for you to re-sign.

[qunabu]

Task linked: HF-162 [Bug]: TEXT(cell, "0.00%") returns values that are wrong by a factor of 100

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	hyperformula-docs	0a2fb42	Commit Preview URL Branch Preview URL	Sep 17 2026, 10:11 PM

[github-actions]

Performance comparison of head (0a2fb42) vs base (c920375)

                                     testName |   base |    head | change
-------------------------------------------------------------------------
                                      Sheet A | 482.34 |  488.46 | +1.27%
                                      Sheet B | 152.44 |  152.68 | +0.16%
                                      Sheet T | 135.22 |  135.67 | +0.33%
                                Column ranges | 467.12 |  463.18 | -0.84%
                                Sorted lookup |  14585 | 13705.9 | -6.03%
Sheet A:  change value, add/remove row/column |  14.65 |      14 | -4.44%
 Sheet B: change value, add/remove row/column | 129.07 |  132.22 | +2.44%
                   Column ranges - add column | 147.94 |  142.81 | -3.47%
                Column ranges - without batch | 447.41 |  437.34 | -2.25%
                        Column ranges - batch |  114.4 |  108.21 | -5.41%

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.32%. Comparing base (c920375) to head (0a2fb42).
⚠️ Report is 1 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1776   +/-   ##
========================================
  Coverage    97.32%   97.32%           
========================================
  Files          195      195           
  Lines        15739    15758   +19     
  Branches      3390     3468   +78     
========================================
+ Hits         15318    15337   +19     
+ Misses         421      413    -8     
- Partials         0        8    +8     

Files with missing lines	Coverage Δ
src/format/format.ts	99.37% <100.00%> (+0.02%)	⬆️
src/format/parser.ts	100.00% <100.00%> (ø)

... and 5 files with indirect coverage changes

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