Add Row Editing Highlight and Tap-to-Edit support for Row selection Mode

[rashmi-thakurr]

Summary

Adds visual row-editing highlight and tap-to-edit support for Row and CellOrRow selection modes, so the active row is clearly indicated while a cell is being edited, matching Windows File Explorer's behavior.

Closes #336

Key Implementation Details

• Editing highlight on the active row: When editing begins, the row receives a highlight (using PointerOverBackground on Windows, _selectionBackground.Opacity on Uno). The highlight follows the editing row as the user navigates with Tab/Enter, and is cleared when editing
  stops.
• Tap-to-edit in Row mode: A second tap on an already-selected row forwards the event to the target cell's BeginCellEditing, enabling File Explorer–style tap-pause-tap-to-rename. Similar forwarding in OnDoubleTapped (skips IsSelected check since the first tap already
  selects).
• Tap-to-edit in CellOrRow mode: A second tap on an already-selected cell starts inline editing without requiring double-click.
• Pointer hover for Row/CellOrRow: Added per-cell pointer hover when individual cells are editable, even if the table is globally read-only.
• Tab wraps row in Row mode: GetNextSlot now treats Tab like Enter when SelectionUnit is Row, so Tab advances to the next row instead of cycling through cells.
• Virtualization safety: PrepareContainerForItemOverride clears stale editing highlight and current-cell borders on recycled containers, and re-applies the highlight when the editing row scrolls back into view.
• Platform-specific rendering: ApplyEditingHighlight uses #if WINDOWS to branch between WinUI 3 (PointerOverBackground brush) and Uno Platform (_selectionBackground.Opacity).
• Alternate-color guard: EnsureAlternateColors skips when _hasEditingHighlight is active, preventing the highlight from being overwritten.

Test Coverage

7 new tests in TableViewRowEditingTests.cs covering: editing highlight in Row mode, editing highlight in CellOrRow mode, pointer hover prerequisites, tap-to-edit prerequisites, virtualization recycling, current-cell state reset, and editing state transitions across rows.

All 173 tests pass (existing + new).

Files Changed

4 files changed, +400 / −6 lines

File	Changes	Description
src/TableView.cs	+64 / −1	Editing highlight fields, PrepareContainerForItemOverride recycling, Tab-wraps-row, highlight movement, SetIsEditing management
src/TableViewCell.cs	+14 / −2	CellOrRow pointer hover, second-tap editing in CellOrRow mode
src/TableViewRow.cs	+75 / −3	Async OnTapped/OnDoubleTapped with tap-to-edit forwarding, ApplyEditingHighlight, EnsureAlternateColors guard
tests/TableViewRowEditingTests.cs	+247 (new)	7 UI tests for row-editing highlight feature