This new default profile is one that doesn't use any tools; it's
completely "naked" and it shouldn't lean into trying to read things from
the current project at hand. Better suited for general topic chats with
the LLM.

PS: Still expecting some wordsmithing here before merging.

Release Notes:

- agent: Added a new default profile called "Manual" that doesn't
include any tools, for general topic chats with the LLM.