expanding and roles

@ will expand for system user tool_result and comment roles. Tune will ignore @ in assistant and tool_call roles. Everything that comes from llm (assistant and tool_call) - ignores @

s: @system - expands
u: @user - expands
a: @assistant - does not expand
tc: @tool_call - does not expand
tr: @tool_result - expands
c: @comment - expands