Tables: Select All then Delete removes a table the document starts with; right-click Delete offers Delete Table again

[marcoarnulfo]

Fixes #1198.

Two separate causes. Ctrl+A in a document that starts with a table puts the selection's start inside the table's first cell, and delete_range only dropped covered tables when the range began outside a table, so Delete/Backspace emptied the cells and left the table. It now handles the other direction too: a range from the very start of a top-level table to a top-level paragraph removes the covered tables and joins what's left. The right-click part is from #694 (284818b), which replaced the old Delete › Rows / Columns / Table submenu with one item that follows the selection, so with just the caret in a cell the menu only offered Delete Cells and there was no way to delete the table from it. Delete is a submenu again (Cells, Columns, Rows, Table), like the Delete button Word shows on right-click; the rest of #694's selection-dependent items are unchanged. Happy to switch to showing only Delete Table next to the selection's own item if you'd rather keep the menu shorter.

Validation:

• tests_typing::select_all_then_delete_removes_tables: fails on main (the table at the document start survives, left: 1, right: 0), passes here
• canvas::tests::a_right_click_in_a_cell_deletes_the_table: fails on main (no Delete Table in the menu with the caret in a cell), passes here; the two existing context-menu tests are updated for the submenu
• cargo clippy -p wordcraft-doc -p wordcraft-engine -p wordcraft-ui-egui --all-targets -- -D warnings, cargo fmt --all -- --check
• (macOS, Apple silicon)

[echelon]

Thanks for the contribution, @marcoarnulfo! This has landed in main. If you haven't already, come join us on Discord: https://discord.gg/artcraft