Fix Kruskal-Wallis test reporting failure with degenerate cases (one observation per group)

[Copilot]

• Merge origin/main into the current branch
• Resolve conflicts in DESCRIPTION (use main's Version: 0.6.3.1)
• Resolve conflicts in NEWS.md (keep both entries: character vector fix from main + Kruskal-Wallis fix from our branch)
• Resolve conflicts in R/report_htest_kruskal.R (use main's cleaner implementation which already includes the degenerate case fix)
• Verify the fix for Kruskal-Wallis degenerate cases is preserved (test file present at tests/testthat/test-report.htest-kruskal.R)
• Complete merge commit (cf33dcd)

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[strengejacke]

@copilot resolve the merge conflicts in this pull request

[Copilot]

@copilot resolve the merge conflicts in this pull request

Merge conflicts resolved in commit cf33dcd. The conflicts were in 3 files:

• DESCRIPTION: Used main's version (0.6.3.1)
• NEWS.md: Merged both entries — main's character vector fix ([Bug]: report fails when a character vector has only one unique value #578) and our Kruskal-Wallis fix (Fail to compute report for Kruskal test in some cases #454)
• R/report_htest_kruskal.R: Used main's version, which already has a cleaner implementation of the same degenerate-case fix