livelog event for finding artifacts

Log artifacts found on the floor, or carried by monsters if hero sees
those monsters do something with them.  Shown to player via #chronicle
and included in dumplog.

For most cases, finding is based on having the artifact object be
formatted for display.  So walking across one won't notice it if pile
size inhibits showing items at its location, even if the artifact is
on top.  Taking stuff out of a container won't notice an artifact if a
subset of the contents chosen by class or BUCX filter doesn't include
it unless player has used ':' to look inside.  Seeing an artifact be
picked up by a monster (even if the monster itself is unseen) or being
dropped (possibly upon death) will find an artifact even if beyond the
normal range of having it be treated as seen up close.  Random treasure
drop items are excluded since they are placed directly on the floor
rather than going into a dying monster's inventory and then dropped
with its other stuff.

src/objnam.c

@@ -1,4 +1,4 @@
-/* NetHack 3.7	objnam.c	$NHDT-Date: 1644347179 2022/02/08 19:06:19 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.343 $ */
+/* NetHack 3.7	objnam.c	$NHDT-Date: 1646652769 2022/03/07 11:32:49 $  $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.347 $ */
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /*-Copyright (c) Robert Patrick Rankin, 2011. */
 /* NetHack may be freely redistributed.  See license for details. */
@@ -513,6 +513,28 @@ xname_flags(
         bknown = obj->bknown;
     }
 
+    /*
+     * Maybe find a previously unseen artifact.
+     *
+     * Assumption 1: if an artifact object is being formatted, it is
+     *  being shown to the hero (on floor, or looking into container,
+     *  or probing a monster, or seeing a monster wield it).
+     * Assumption 2: if in a pile that has been stepped on, the
+     *  artifact won't be noticed for cases where the pile to too deep
+     *  to be auto-shown, unless the player explicitly looks at that
+     *  spot (via ':').  Might need to make an exception somehow (at
+     *  the point where the decision whether to auto-show gets made?)
+     *  when an artifact is on the top of the pile.
+     * Assumption 3: since this is used for livelog events, not being
+     *  100% correct won't negatively affect the player's current game.
+     *
+     * We use the real obj->dknown rather than the override_ID variant
+     * so that wizard-mode ^I doesn't cause a not-yet-seen artifact in
+     * inventory (picked up while blind, still blind) to become found.
+     */
+    if (obj->oartifact && obj->dknown)
+        find_artifact(obj);
+
     if (obj_is_pname(obj))
         goto nameit;
     switch (obj->oclass) {