[sedax90]

Summary

• Every other row of every data grid (table tab, query results, key tab) gets a light shade, on by default as on macOS.
• Preferences, Data Browser, gains Show Alternate Row Backgrounds (GSettings key show-alternate-rows, default true). Each open grid follows the key live.
• GTK 4.22 has no stripe API, and :nth-child cannot stripe recycled rows. Each cell's child takes a class from its row's position, so stripes stay right after scrolling and when a row is added above.
• The shade is a static rule in style.css on var(--view-fg-color), stronger under high contrast, and stays off a selected row. No runtime CSS provider.
• The cell padding moves to the cell's child, as in libadwaita's file chooser, so the stripe fills the cell. Row heights and column widths do not change.
• The filler column gets an empty child, so the stripe reaches the right edge instead of stopping at the last column.
• Fixed in the first version: the stripe rule was installed by the SQL editor, so a table or key tab opened without an editor had no stripes, and the switch stopped working once the last editor closed.

Test plan

• every_other_row_is_striped_out_to_the_filler (the row number column, both data columns and the filler) and open_grids_follow_the_stripes_preference fail on the first version.
• a_row_added_above_moves_the_stripes and recycled_rows_take_the_stripe_of_their_new_position (300 rows, scrolled to row 250) check that the stripe follows the position.
• preference_rows_are_bound, plus defaults_match_schema and show_alternate_rows_round_trip in the storage tests.
• CI runs the build, tests and lint. No local Linux build was available, so there are no screenshots.