feat(options-list): add a select-all header checkbox

[mt8]

Summary

• Add a tri-state header checkbox to the Options table that selects/deselects every non-protected visible row in one click. Indeterminate state kicks in when some (but not all) selectable rows are selected.
• WordPress-Core accessor rows stay unselectable — the header toggle never flips them.
• Japanese translation shipped ("このページのすべてのオプションを選択").

Closes #118

Implementation note

The header uses a native `<input type="checkbox">` with a ref so the `indeterminate` DOM property can be flipped from `useEffect`. `@wordpress/components` `CheckboxControl` does not expose that property.

Test plan

• Click the header checkbox → every non-protected visible row flips to selected; the bulk-action buttons enable.
• Individually deselect one row → header becomes indeterminate.
• Click again from indeterminate or fully-checked state → all selectable rows deselected.
• Protected (WordPress-Core) rows never toggle via the header.
• Japanese locale renders the aria-label translation.
• CI green.