[FEATURE] Mods on desktop: let a plugin draw the AbovePrompt band without its grey plate

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

Problem
On the desktop app (Code tab), the AbovePrompt band always wraps a mod's content in a grey plate. I built a mod with an animated companion: EVE from WALL·E, a ~96 px SVG that sits above the prompt and reacts to what Claude is doing. Inside the plate she reads as a widget in a box rather than a character next to the prompt.

What I measured on the dark theme:

The plate is #212121 and the page is #151515.
The plate's padding is about 10 px on the sides and 13 px on the top and bottom.
What I tried
backgroundColor on the mod's root Box. Paints only the row, not the plate.
Negative marginX with matching paddingX. The row covers the plate's sides. This works.
Negative marginY. Changes nothing: the band clips its rows vertically, so the top and bottom strips always stay.
An empty position: "absolute" Box placed first, with negative offsets. It paints over the in-flow siblings that follow it and hides the companion. position: "relative" on those siblings doesn't bring them back on top.
Plain <Svg>. Stays transparent and runs SMIL, which is great. The plate is the only thing in the way.

Proposed Solution

Proposed solution
Add an option on the band, for example a prop on the root Box or a field in the render result:

chrome?: 'plate' | 'none' | 'glass'
plate is today's look.
none draws only the mod's tree on the page background.
glass would be a translucent or blurred plate, if that fits the design system.

Alternative Solutions

Alternatives
Painting the plate with the page color. This hides only its sides.
The Spinner row. It exists only while a turn runs.
PromptHint and SessionMode. These don't draw an Svg on desktop.

Priority

Medium - Would be very helpful

Feature Category

Other

Use Case Example

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Additional Context

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