[AsafMah]

Description

Column headers weren't keyboard-focusable (IsTabStop was False in the default style), so keyboard and screen reader users couldn't sort, group or filter. (Cells already expose their column header through TableItemPattern, so header names were announced, but the headers' actions were mouse-only.)

• The header row is one tab stop (TabFocusNavigation="Once"), with Left/Right moving between headers (XYFocusKeyboardNavigation).
• On a header, Enter or Space sorts, cycling like a click; Ctrl adds to the existing sort, like Ctrl+click.
• Alt+Down, Shift+F10 or the Menu key opens the column's options flyout. Keyboard context requests are told apart from right-clicks by having no pointer position, so right-click keeps following UseRightClickForColumnFilter.

Related Issue

None opened.

Type of Change

• 🐛 Bug fix
• ✨ New feature
• 📝 Documentation update
• ♻️ Refactor
• 🧪 Test
• 🔧 Chore / maintenance

Checklist

• This PR is not from my main branch
• Tested with WinUI target (partly: in an app, via UI Automation the headers now report as keyboard-focusable and the arrow keys move focus between them; Enter/Space and Shift+F10 are not yet exercised by hand)
• Tested with Uno Platform target (not tested; XYFocusKeyboardNavigation is set with the win: prefix)
• Unit / integration tests added or updated (none added; the existing suite passes locally except one test that also fails on main on my machine)
• Documentation updated to reflect changes (accessibility.md)
• Code follows the project's coding conventions

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