Add table header, date range, status tag, action item, and scope helpers

[Copilot]

Adds a batch of missing DSL helpers for testing Active Admin pages — covering table headers, date range filters, status tags, action item links, table scopes, and sidebar scoping.

New matchers

• have_fields_date_range(label, from:, to:, exact:) — asserts a filter_date_range input pair exists with expected values
• have_table_header(text, column:, sortable:, sort_direction:) — asserts a thead > tr > th.col with optional sortable/sort-direction class checks
• have_action_item_link(title, exact:, href:) — asserts an action item <a> with optional href attribute matching
• have_status_tag(type, **options) — asserts span.status_tag.<type>

New finders

• within_table_footer — scopes within tfoot > tr
• find_table_header(text, options) — returns the matching header node
• find_action_item(title, exact:) — returns the matching action item node
• within_action_item_dropdown — scopes within .dropdown_menu_list_wrapper

New actions

• click_table_scope(text) — clicks a scope tab by exact text
• click_table_header(text, options) — clicks the sort link inside a header

Updated

• table_header_selector now accepts optional text, column:, sortable:, sort_direction: — returns a fully qualified thead > tr > th.col.col-<name>[.sortable][.sorted-asc|desc] selector
• within_sidebar replaced within_panel traversal with direct ancestor('.sidebar_section') lookup — more robust against markup variations
• have_table_scope gains an optional positional title arg and a selected: keyword, e.g.:

expect(page).to have_table_scope('Active')
expect(page).to have_table_scope('Active', selected: true)
# legacy no-title form still works
expect(page).to have_table_scope(exact_text: 'Active', selected: false)