Two documents catch up with the save rule

The quickstart's bug-reporting section told a player to save the game and send the file;
in a Competitive multiplayer game that button now waits for the end, so it says so and says
to note the Day and Stage instead. The route table in multiplayer.md gains `/api/save`,
which had been in the code since 0.8.0.10 and never in the table. No code, no version.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FrCWubm9GAftYCm2hWdKwK

docs/quickstart.md

@@ -190,7 +190,9 @@ Please do report anything that looks like a bug or an area to be improved.
 - **What you expected versus what happened**, with the Day and Stage. "Day 2 Stage 9, train 5 had
   no coaches" is worth more than "passengers seem broken".
 - **Save the game** (the **Save replay** button) and send the file. A save is the seed and the moves
-  made, so it replays exactly and the problem can be looked at directly.
+  made, so it replays exactly and the problem can be looked at directly. In a Competitive
+  multiplayer game the button waits until the game is over, because the file carries the seed and
+  the seed is every rival's hand; note the Day and Stage and save it at the end.
 - **Anything the screen did not explain.** If you had to guess a rule, that is worth saying even
   when the game was right.
 - **Anything you went looking for and could not find.**