Backdrop theme gains colorScheme, plus upload and connector helpers

What

The backdrop is the theme behind the screen that mods (add-ons that change how Claude Code looks) can set. It used to carry only an id and an optional glass setting. It can now also carry a colorScheme.

• colorScheme is optional and must be light or dark. It is accepted by the theme argument check and carried on the ui.backdrop mod event and in the backdrop state.
• Two new internal tools are registered, NoteSavedUploads and RemoveDeletedUploads.
• The address used for file uploads can now end with a session_received=yes or session_received=no setting.
• New helpers build claude.ai connector addresses that open with modal=add-custom-connector, the screen for adding a custom connector.
• A prompt fragment about reading only part of a page was added.

Why

Mods can now say whether their backdrop is meant for a light or a dark look. The upload tools and connector links are small additions that do not change what you see yet.