chore: strip remaining pre-fork version references

Second pass — removes chat-switchboard version numbers from config
field docs, section headers, file headers, and test comments. These
were pre-fork version tags that don't apply to switchboard-core.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/events/bus_test.go

@@ -117,10 +117,10 @@ func TestRouteFor(t *testing.T) {
 		// Extension lifecycle
 		{"extension.loaded", DirLocal},
 		{"extension.error", DirLocal},
-		// Realtime (v0.5.0)
+		// Realtime
 		{"realtime.chat.message", DirToClient},
 		{"realtime.custom.event", DirToClient},
-		// Room management (v0.5.0)
+		// Room management
 		{"room.subscribe", DirFromClient},
 		{"room.unsubscribe", DirFromClient},
 	}