A point names a moment in a session at which a message can be injected or
a probe asked. fg_after_item(k) is the moment just after the moderator's
line for item k of the guide, before any participant answers it.
fg_before_turn(t) is the moment just before the t-th participant turn
of the session, counting from 1 across all questions, before the speaker
of that turn is chosen. A probe may also be asked at "start", before the
moderator's first line, or at "end", after the last message, the
closing line included, and before the final summary. A probe or an
injection may be placed at "before_closing", after the last discussion
item and the call-ons that follow it and before the closing line; in a
guide without a closing item it comes just before "end".
Details
Guide items are numbered in the order the session runs them: with
guide = c(Opening = 1, Icebreaker = 1, Engagement = 2, Exploration = 3, Closing = 1), item 4 is the second engagement question.
Participant turns count every reply, those that answer the moderator's
call-on lines among them (see call_on_silent in run_focus_group()).
When fg_before_turn(t) falls on the reply to a call-on line, it comes
after that line. A custom turn-taking flow can end the discussion of an
item by choosing no participant (NULL) or the moderator; that choice is
not a turn and has no routing record. The point has then already come, so
when call-ons follow, fg_before_turn(t) falls before the call-on line
whose reply is turn t.
