Components.AI: Decide and implement clipboard-image attachment paste

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

`ClipboardEventArgs` does not expose clipboard image items, so paste-to-attach requires JS interop and its value relative to drag-and-drop remains undecided.

### Describe the solution you'd like

Decide whether clipboard-image paste belongs in the built-in experience. If adopted, add only the minimal interop needed and feed pasted images through the normal validation, chip, transfer, and removal pipeline.

### Additional context

Leaf task for #68227 requirement D5 and open design decision 6.

Start with requirement D5 in issue #68227 and open design decision 6; the issue names no source files or tests. First decide whether clipboard-image paste belongs in the built-in experience and how it compares with drag-and-drop. If adopted, done means minimal interop feeds pasted images through validation, chip, transfer, and removal.

Written by the indexing model from the issue text.