adventure: tell Pete when a story-grade treasure is found

A treasure that earns a public room announce now also files a treasure_found
fact, so Pete can count it on the finder's trophy case. The emit rides inside
announceTreasureToRoom, reusing the RoomAnnounce != "" gate as the newsworthiness
filter — a copper-piece pickup never becomes news, and a reversed auto-swap never
emits, because the announce it shares is cancelled on undo.

The realm's first finder of a given treasure is a priority hoard; a later finder
of the same item is a bulletin, keyed on the treasure across the realm via
claimRealmFirst, the same first/repeat split zone_first uses. The item name rides
in stakes and the tier-derived rarity in outcome.

treasure_found is a new event_type, so Pete's ingest must deploy first or the
first finds park on the retry ladder forever.

internal/plugin/adventure.go

@@ -1383,6 +1383,10 @@ func (p *AdventurePlugin) announceTreasureToRoom(char *AdventureCharacter, def *
 	if def == nil || def.RoomAnnounce == "" {
 		return
 	}
+	// The same story-grade gate feeds Pete's trophy case. Emit before the
+	// games-room check so a find is still recorded as news even when no room is
+	// configured to announce it in.
+	emitTreasureFound(char.UserID, def, loc)
 	gr := gamesRoom()
 	if gr == "" {
 		return