Add immutable options for DataTable import and export

[jochenwezel]

Summary

• add immutable nested ReadOptions and WriteOptions to both CompuMaster.Data EPPlus editions
• add explicit *WithOptions entry points while keeping the existing static API and legacy defaults unchanged
• make worksheet header discovery honor the configured zero-based start row when filling an existing DataTable
• keep the generated Polyform source and tests synchronized with the FixCalcs edition

Validation

• ./tools/check-api-docs.ps1 (0 missing documentation, 0 missing inheritdoc)
• focused Data API tests: 15 passed on .NET Framework 4.8 and 15 passed on .NET 8
• full CI_CD suite: 244 passed and 15 skipped per target framework; 5 existing Microsoft Excel process-cleanup tests failed because one user-owned EXCEL.EXE process was already running before the suite. The process was intentionally not terminated.

No HTML preview behavior was changed.

[github-actions]

Unit Test Statistics (ubuntu-latest) CompuMaster.MsExcelComInteropTest.dll

2 tests  ±0   2 ✅ ±0   0s ⏱️ ±0s
1 suites ±0   0 💤 ±0 
1 files   ±0   0 ❌ ±0 

Results for commit 993f53b. ± Comparison against base commit f83d47e.

[github-actions]

Unit Test Statistics (ubuntu-latest) CompuMaster.Excel.Test.dll

58 tests  +3   58 ✅ +3   2s ⏱️ ±0s
 1 suites ±0    0 💤 ±0 
 1 files   ±0    0 ❌ ±0 

Results for commit 993f53b. ± Comparison against base commit f83d47e.

[github-actions]

Unit Test Statistics (ubuntu-latest) CompuMaster.Excel.TestFreeSpireXls.dll

6 tests  ±0   6 ✅ ±0   0s ⏱️ -1s
1 suites ±0   0 💤 ±0 
1 files   ±0   0 ❌ ±0 

Results for commit 993f53b. ± Comparison against base commit f83d47e.

[github-actions]

Unit Test Statistics (ubuntu-latest) CompuMaster.Excel.TestSpireXls.dll

6 tests  ±0   6 ✅ ±0   0s ⏱️ ±0s
1 suites ±0   0 💤 ±0 
1 files   ±0   0 ❌ ±0 

Results for commit 993f53b. ± Comparison against base commit f83d47e.

[github-actions]

Unit Test Statistics (macos-latest) CompuMaster.MsExcelComInteropTest.dll

2 tests  ±0   2 ✅ ±0   0s ⏱️ ±0s
1 suites ±0   0 💤 ±0 
1 files   ±0   0 ❌ ±0 

Results for commit 993f53b. ± Comparison against base commit f83d47e.

[github-actions]

Unit Test Statistics (macos-latest) CompuMaster.Excel.Test.dll

58 tests  +3   58 ✅ +3   2s ⏱️ -1s
 1 suites ±0    0 💤 ±0 
 1 files   ±0    0 ❌ ±0 

Results for commit 993f53b. ± Comparison against base commit f83d47e.

[github-actions]

Unit Test Statistics (macos-latest) CompuMaster.Excel.TestFreeSpireXls.dll

6 tests  ±0   6 ✅ ±0   1s ⏱️ -1s
1 suites ±0   0 💤 ±0 
1 files   ±0   0 ❌ ±0 

Results for commit 993f53b. ± Comparison against base commit f83d47e.

[github-actions]

Unit Test Statistics (macos-latest) CompuMaster.Excel.TestSpireXls.dll

6 tests  ±0   6 ✅ ±0   0s ⏱️ ±0s
1 suites ±0   0 💤 ±0 
1 files   ±0   0 ❌ ±0 

Results for commit 993f53b. ± Comparison against base commit f83d47e.

[github-actions]

Unit Test Statistics (windows-latest) CompuMaster.MsExcelComInteropTest.dll

2 tests  ±0   2 ✅ ±0   0s ⏱️ ±0s
1 suites ±0   0 💤 ±0 
1 files   ±0   0 ❌ ±0 

Results for commit 993f53b. ± Comparison against base commit f83d47e.

[github-actions]

Unit Test Statistics (windows-latest) CompuMaster.Excel.Test.dll

266 tests  +3   266 ✅ +3   41s ⏱️ -1s
  1 suites ±0     0 💤 ±0 
  1 files   ±0     0 ❌ ±0 

Results for commit 993f53b. ± Comparison against base commit f83d47e.

[github-actions]

Unit Test Statistics (windows-latest) CompuMaster.Excel.TestFreeSpireXls.dll

75 tests  ±0   75 ✅ ±0   19s ⏱️ ±0s
 1 suites ±0    0 💤 ±0 
 1 files   ±0    0 ❌ ±0 

Results for commit 993f53b. ± Comparison against base commit f83d47e.

[github-actions]

Unit Test Statistics (windows-latest) CompuMaster.Excel.TestSpireXls.dll

77 tests  ±0   77 ✅ ±0   19s ⏱️ ±0s
 1 suites ±0    0 💤 ±0 
 1 files   ±0    0 ❌ ±0 

Results for commit 993f53b. ± Comparison against base commit f83d47e.