fix(linux): keyboard sort, named fields, focus hand-off, announcements

[datlechin]

• Grid cell menu: Sort Ascending, Sort Descending, Clear Sort, Reset Column Width, since header titles take no focus. Clear Sort reaches the browse tab's server sort.
• Names: filter strip fields and rule rows (WHERE and Match label their fields), cell editors (the column name), browse and editor grids, saved queries search, SQL Preview. History rows and export Stop/progress are tied to their row title.
• Focus: disabling or hiding the focused control hands focus on (pager to the nearest usable button, Save to Stop Saving and back, Discard to the grid, closing the filter strip back where it came from); an error page focuses Try Again.
• Announcements through a new a11y::announce helper: stale banner, error page, count failure, run summary, find match count and regex errors, connection banner, page range, pending count, saving, structure pending label.
• Invalid state and message sit on the focused field (show_invalid), including Add Index and Add Foreign Key.
• F6 is in the accelerators and the shortcuts dialog. Ctrl+F opens or focuses the filter strip instead of toggling it; the button uses browse.toggle-filter.
• Deleted-row text uses the full error colour (about 4.9:1); unsaved tabs say so in the tooltip.
• Escape hides a visible popup on the editor before it stops a run.
• The accessibility audit scenarios also open the filter strip with a rule, an inline cell editor, and the Add Index and Add Foreign Key forms.
• Skipped: tooltips only on cut-off text, a named "Status" header (GTK 4.22 can't name one without showing it), connection colour in the row description.