Remove internal reasoning from copied message text to avoidleaking implementation details or developer-only when a
user content from the chat- In chat_pagecopyMessage, cleaning steps to:
- <details type="ing">...</details blocks
- <think>think> and <ing>...</reason> tags
- trim leftover whitespace before writing to the clipboard
- In assistant_message_widget._buildSegmentedContent, remove an
unused hasMediaAbove calculation and a conditional spacer that added
extra top padding before reasoning tiles. This simplifies rendering
logic and avoids relying on removed spacing behavior.