Right-click Copy copies the whole message instead of the selection; pasted text retains dark background

Description

In the Claude Code desktop app, copying text from an assistant message has two problems:

1. Right-click "Copy" ignores the selection and copies the whole message. When I highlight only a portion of text inside a message and use the right-click context menu → Copy, the entire message is copied instead of just the highlighted selection.
2. Copied body text carries the dark-theme background color. When pasting the copied text into another app (document, email field, etc.), the dark/black background styling comes along, so the pasted text is hard to read on a light background.

Steps to reproduce

1. In a conversation, select (highlight) part of the text inside an assistant message.
2. Right-click and choose Copy.
3. Paste into another application.

Expected

• Only the highlighted selection is copied.
• Pasted text is plain (or at least does not carry the dark background color).

Actual

• The whole message is copied, not just the selection.
• Pasted text includes the dark/black background styling.

Notes / workaround

• Cmd + C on a highlighted selection does copy only the selection, but the right-click context-menu "Copy" still grabs the entire message.
• The background-color issue persists with rich-text paste regardless of how the copy is triggered.

Environment

• Claude Code desktop app
• macOS (Darwin 25.4.0)