Message action toolbar overlaps message text on hover

[andrii-i]

Problem

When hovering over a message in Jupyter Chat, the message action toolbar can appear overlaid on top of the message text. This reduces text readability, makes the action buttons hard to notice, and gives the UI a broken appearance.

Proposed Solution

Redesign the message action toolbar so it doesn't interfere with text readability. Two possible approaches:

1. Position the toolbar so it never overlaps message text (e.g., above the message bubble or in a dedicated gutter)
2. If overlapping is unavoidable, give the toolbar a solid/opaque background so buttons are clearly distinguishable from the text beneath (see screenshot below as reference)

[nakul-py]

Position the toolbar so it never overlaps message text (e.g., above the message bubble or in a dedicated gutter)

Sounds good 👍.

[nakul-py]

@brichet working on this if you don't mind.