feat(calc): add implicit intersection and fix regex criteria anchoring

[jpoz]

PR Details

Description

This PR implements two related fixes for the calculation engine:

1. Implicit Intersection: Adds implicitIntersect method that resolves matrix arguments to scalar values based on the formula cell's row position. This matches Excel's behavior where range references in non-array formulas resolve to the cell in the same row as the formula. Applied to ABS, ISNUMBER, and IF functions.

2. Regex Criteria Anchoring Fix: Moves ^/$ anchor insertion from formulaCriteriaParser to formulaCriteriaEval. The previous approach (anchoring at parse time) interfered with numeric criteria parsing since "^5$" cannot convert to a number. Anchoring at eval time preserves correct ToNumber() behavior while still enforcing exact matching in SUMIF/COUNTIF.

3. ISNUMBER matrix bug fix: The previous matrix handling code in ISNUMBER had a missing else branch, causing it to append both true and false for number cells, corrupting the output matrix. Replaced with implicitIntersect for correct scalar resolution.

Related Issue

Fixes implicit intersection behavior for scalar functions receiving range/matrix arguments.

Motivation and Context

When a whole-column or range reference is passed to a scalar function like ABS(A1:A5), Excel resolves it to the single cell in the same row as the formula cell (implicit intersection). Without this fix, the calculation engine could not handle these common spreadsheet patterns correctly. The regex anchoring fix ensures criteria-based functions (SUMIF, COUNTIF, etc.) correctly match exact values without breaking numeric criteria handling.

How Has This Been Tested

• Added TestCalcImplicitIntersect: validates ABS, ISNUMBER, and IF with range references across multiple rows, confirming each resolves to the correct row via implicit intersection (11 assertions)
• Added TestCalcCriteriaRegexpAnchoring: validates exact matching, wildcard patterns (*, ?), and numeric criteria for SUMIF/COUNTIF
• All existing tests pass including TestCalcSUMIFExactMatch, TestCalcAVERAGEIF, and TestCalcCellValue

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.56%. Comparing base (37b6a8f) to head (8611d37).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2268   +/-   ##
=======================================
  Coverage   99.56%   99.56%           
=======================================
  Files          32       32           
  Lines       26316    26322    +6     
=======================================
+ Hits        26201    26207    +6     
  Misses         60       60           
  Partials       55       55           

Flag	Coverage Δ
unittests	99.56% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[Copilot]

Pull request overview

This PR updates the calculation engine to better match Excel semantics by adding implicit intersection handling for certain scalar functions and adjusting how criteria regex anchoring is applied during SUMIF/COUNTIF-style evaluations.

Changes:

• Added implicitIntersect helper and applied it to ABS, ISNUMBER, and IF to resolve matrix/range arguments to scalars.
• Moved regex ^/$ anchoring behavior into formulaCriteriaEval for criteriaRegexp.
• Added tests covering implicit intersection and criteria regex anchoring behavior.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
calc.go	Adds implicitIntersect, applies it to functions, and changes regex anchoring logic in criteria evaluation.
calc_test.go	Adds new tests for implicit intersection and criteria anchoring behavior.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[xuri]

Thanks for your contribution.