core/cli: keep a prompt notification on screen

A prompt notification went out with the library defaults: the notification
server's own expiry. A desktop server drops such a notification after a few
seconds, so the announcement of a blocked turn had usually slid into the
notification tray by the time the human looked back.

It now goes out without expiry (`timeout=0`, the freedesktop value for "until
dismissed"). Urgency is left alone: measured on KDE Plasma, `critical` keeps the
notification up just the same, but paints it as urgent and asks the platform's
Focus mode to let it through — decoration a prompt does not need. Dismissing is
already the prompt's own job once it is answered, so nothing lingers.

src/plyngent/cli/notify.py

@@ -60,6 +60,14 @@ _BUTTONS: tuple[tuple[str, str], ...] = (
 _MAX_TITLE = 80
 _MAX_MESSAGE = 200
 
+#: Seconds a desktop notification may stay up; ``0`` is the freedesktop value
+#: for "until dismissed" (``-1`` would hand the notification server's default
+#: back, which is a few seconds — after that the notification collapses into
+#: the tray, where nobody waiting on a prompt looks). Urgency stays at the
+#: library default: ``critical`` keeps the notification up just the same, but
+#: paints it as urgent and asks the platform's Focus mode to let it through.
+_NO_EXPIRY = 0
+
 
 def _clean(text: str, limit: int) -> str:
     """One line, no control characters, truncated to *limit* characters."""
@@ -171,6 +179,11 @@ class DesktopNotifierChannel:
                 send(
                     title=request.title,
                     message=request.message,
+                    # A prompt holds the turn until it is answered, so the
+                    # notification must still be on screen when the human looks
+                    # back. Dismissing is the prompt's own job once it is
+                    # answered, so nothing lingers.
+                    timeout=_NO_EXPIRY,
                     buttons=buttons,
                     reply_field=reply,
                 )

typings/desktop_notifier/__init__.pyi

@@ -22,6 +22,11 @@ class Capability(Enum):
     THREAD = ...
     TIMEOUT = ...
 
+class Urgency(Enum):
+    Critical = ...
+    Normal = ...
+    Low = ...
+
 class Button:
     def __init__(
         self,
@@ -50,7 +55,7 @@ class DesktopNotifier:
         self,
         title: str,
         message: str,
-        urgency: Any = ...,
+        urgency: Urgency = ...,
         icon: Any = ...,
         buttons: Sequence[Button] = ...,
         reply_field: ReplyField | None = None,