Move the keyboard shortcut mapping into the pure post-options service so the
React component is a thin adapter and the Escape/ArrowDown decisions are unit
and property testable. DRY the duplicated post-options acceptance steps behind
two helpers, and add property tests for the explorer URL, menu-item shape,
state transitions, key command, and rendered markup.
The createElement post-options component and service stay scannable by
mutate4javascript; the JSX call sites (post-feed-item, profile) are unchanged
except for rendering the shared menu.
By refactorer.
