Message right-click menu now appears with disabled items when no text is selected

What changed

Right-clicking inside the chat message area, citations, and agent session messages now always shows the "Copy" / "Quote" context menu. Previously the menu was only opened when there was an active text selection. The items are disabled when nothing is selected, so the menu is discoverable but inert.

Why this matters to the user

Before this change, right-clicking on plain (non-selected) message text did nothing. After this change, the menu shows up but both actions appear greyed out until the user selects some text. The eventual behavior of "Copy" / "Quote" once a selection exists is unchanged.

What the user should do

Nothing — automatic. The change is purely additive (discoverability) and the keyboard / clipboard behavior of a real selection is identical to v1.

Notes for release manager

Renamed ContextMenu (the selection-aware wrapper) to SelectionContextMenu internally — no user-visible impact, just call out if release notes ever reference component names.