Proper demo playback cleanup and state reset

- Extract SVD_CleanupPlayback for shared cleanup logic
- Called on demo end (SVD_PlaybackFrame) and manual stop
- Frees zombie client slots, saved configstrings, file handle
- Clears sv_demoplaying cvar so game module exits demo mode
- Hook into SV_Shutdown to clean up on server shutdown/map change
- Allows playing another demo after one finishes

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

code/server/sv_init.c

@@ -667,6 +667,14 @@ void SV_Shutdown( char *finalmsg ) {
 
 	Com_Printf( "----- Server Shutdown -----\n" );
 
+	// clean up any active demo recording/playback
+	if ( SVD_IsRecording() ) {
+		SVD_StopRecord_f();
+	}
+	if ( SVD_IsPlaying() ) {
+		SVD_StopPlay_f();
+	}
+
 	if ( svs.clients && !com_errorEntered ) {
 		SV_FinalMessage( finalmsg );
 	}

code/server/sv_netdemo.c

@@ -735,11 +735,10 @@ void SVD_Play_f( void ) {
 	demo.needConfigstrings = qtrue;
 }
 
-void SVD_StopPlay_f( void ) {
+static void SVD_CleanupPlayback( void ) {
 	int i;
 
 	if ( !demo.playing ) {
-		Com_Printf( "Not playing a server demo.\n" );
 		return;
 	}
 
@@ -751,9 +750,25 @@ void SVD_StopPlay_f( void ) {
 			Z_Free( demo.savedConfigstrings[i] );
 		}
 	}
-	memset( &demo, 0, sizeof(demo) );
 
+	// free zombie client slots
+	for ( i = 0; i < demo.playMaxClients; i++ ) {
+		if ( svs.clients[i].state == CS_ZOMBIE ) {
+			svs.clients[i].state = CS_FREE;
+		}
+	}
+
+	memset( &demo, 0, sizeof(demo) );
 	Cvar_Set( "sv_demoplaying", "0" );
+}
+
+void SVD_StopPlay_f( void ) {
+	if ( !demo.playing ) {
+		Com_Printf( "Not playing a server demo.\n" );
+		return;
+	}
+
+	SVD_CleanupPlayback();
 	Com_Printf( "Server demo playback stopped.\n" );
 }
 
@@ -773,8 +788,8 @@ qboolean SVD_PlaybackFrame( void ) {
 	}
 
 	if ( !SVD_ReadFrame( demo.playFile ) ) {
-		demo.endOfDemo = qtrue;
 		Com_Printf( "Server demo playback finished.\n" );
+		SVD_CleanupPlayback();
 		return qfalse;
 	}