Name and order the tool code

Every package-level name of the tools starts with tool: the Toolbox, its
interfaces ToolLog and ToolChat, the argument types, the head and tail
buffer, and the clip helpers. The interfaces chatLog and chatReader read
as parts of the chat, but only the tools use them.

The declarations of tools.go follow the order of the go-code skill. The
behavior does not change.

Issue: 947bddb