Bots that open the conversation

A bot that only answers is not negotiating, it is a form to fill in. propose()
works from the plan the power has already made: what it wants this turn, where
that will not work alone, and who could make it work. Help taking something
defended first, then a quiet border over ground neither of them owns, then
peace when a neighbour is over your centres and your ambitions are elsewhere.
Three a turn at most, or six powers talking at once is a mailstorm.

Each overture carries what the power says, so it reaches a human as a message
rather than as a form.

A power will offer a quiet border to somebody it is attacking somewhere else,
and that is on purpose. Marching on French Belgium while suggesting both
sides leave Burgundy alone is not a lie and not incoherent -- a promise about
Burgundy is a promise about Burgundy, and it will be kept to the letter by
somebody robbing you at the same moment. A test asserted the opposite and the
test was wrong: refusing that offer would be playing a politer game than this
one. Asking the power you are attacking to help you, or offering it peace
while your orders say otherwise, are different things and are both refused.

Nothing here promises any of it will be kept. Whether the power still wants
the deal when orders are due is settled in settleUp, and the answer is
sometimes no.

README.md

@@ -141,7 +141,27 @@ power that has been lied to four times a high cost of retaliating, because it
 has been scrupulous itself and is still well thought of, which is exactly
 backwards. An ally who has already betrayed you is worth nothing to protect.
 
+Bots open negotiations rather than only answering them. `propose()` works
+from the plan the power has already made: it decides what it wants to do this
+turn, notices where that will not work alone, and goes looking for somebody
+who could make it work. Help taking something defended, first; then a quiet
+border over ground neither of them owns; then peace outright, when a
+neighbour is over your centres and your ambitions are elsewhere. Three
+approaches a turn at most, because six powers all talking at once is a
+mailstorm rather than a negotiation.
+
+Each overture carries what the power actually says, so it can be put in front
+of a human as a message rather than as a form.
+
+**A power will offer a quiet border to somebody it is attacking somewhere
+else**, and that is deliberate. Germany marching on French Belgium while
+suggesting both sides leave Burgundy alone is not a lie and not incoherent: a
+promise about Burgundy is a promise about Burgundy, and it will be kept to
+the letter by somebody who is robbing you at the same moment. A bot that
+refused to make that offer would be playing a politer game than this one. It
+will not, however, ask the power it is attacking to *help*, or offer it peace
+while the orders say otherwise.
+
 ## Still to build
 
-- proposals: bots opening a negotiation rather than only answering one
 - the map, the orders, the music, the battle sound, the four endings