Components.AI: Make decorator actions accessible on hover, tap, focus, and keyboard

### Is your feature request related to a problem? Please describe the problem.

Hover-only action disclosure excludes touch and keyboard users, and revealing controls can cause layout movement.

### Describe the solution you'd like

Reserve decorator-row space, reveal the shipped default on hover/tap/focus without shifting content, keep controls in the accessibility tree with distinct names, and provide keyboard traversal compatible with virtualization.

### Additional context

Leaf task for #68227 requirements F4 and H6.

Start by reading the Components.AI context and requirements F4 and H6 in issue #68227, then locate the corresponding implementation and tests. Done means decorator actions remain accessible on hover, tap, focus, and keyboard without layout movement, retain distinct accessible names, and support keyboard traversal with virtualization.

Written by the indexing model from the issue text.