ui/curses: wait for keys instead of polling

The main loop slept 100 ms whenever no key was pending, so keys took
up to a tick to register and every screen woke ten times a second.
Each view now declares how often it needs idle(): the game view keeps
its 100 ms tick, while menus wait for a key. getch() blocks for that
long, so keys register at once, and over 15 s in the roster menu the
process goes from about 300 wake-ups to 6.

pqcli/ui/curses/views/base_view.py

@@ -2,6 +2,9 @@ import curses
 
 
 class BaseView:
+    # How often idle() runs, in milliseconds; None waits for a key.
+    idle_interval: int | None = None
+
     def __init__(self, screen: curses.window) -> None:
         self.screen = screen