Add path copy buttons for Text comparison results in HTML reports

[Widthdom]

Summary

• add IL-style two-file copy buttons to TextMatch and TextMismatch results in HTML reports
• copy the quoted absolute paths of the old/new files associated with those Text comparison results using native Windows, macOS, or Linux path conventions
• show the buttons consistently in Unchanged, Modified, and repeated timestamp-warning rows
• share the path-pair icon between IL and Text buttons while retaining category-specific behavior and tooltips
• update the sample HTML report, English/Japanese user guide, changelog, and automated coverage

Why

Text comparison results in HTML reports exposed only the relative file path, so opening the corresponding old/new files in an external text-based diff tool required manually locating both files. This brings the existing IL path-copy workflow to TextMatch and TextMismatch results.

User impact

Users can copy both quoted absolute old/new file paths for Text comparison results with one click directly from the HTML report's Diff Detail column. Existing IL path-copy behavior remains unchanged.

Validation

• dotnet test FolderDiffIL4DotNet.Tests/FolderDiffIL4DotNet.Tests.csproj -c Release --no-restore --filter 'FullyQualifiedName~HtmlReportGenerateServiceTests' — 164 passed
• npm run test:js -- --runInBand JsTests/diff_report.test.js — 127 passed
• dotnet test FolderDiffIL4DotNet.Tests/FolderDiffIL4DotNet.Tests.csproj -c Release --no-restore — 2061 passed, 1 skipped
• npm run test:js -- --runInBand — 190 passed
• git diff --check