Cleanup: fix logger warnings introduced by SDL 3 migration

- logger.c:103 log_write_raw() missing return in unreachable
  assert(0) branch; clang flagged the missing return statement.
- logger.c:191 SDL_GetTicks() now returns Uint64 in SDL 3; widen the
  printf format from %d to %llu and bump the local buffer size.

Build is clean. Remaining warnings (strncat-size in a_wave.c,
invalid-source-encoding in a_midifile.c) are pre-2007 code-style
issues unrelated to SDL.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

logger.c

@@ -100,6 +100,7 @@ static inline int log_write_raw(int target, const char *text)
 		/* We should never get here. */
 		assert(0);
 	}
+	return 0;
 }
 
 
@@ -187,8 +188,9 @@ static inline void put_timestamp(int level)
 {
 	if(l_targets[l_levels[level].target].flags & LOG_TIMESTAMP)
 	{
-		char buf[16];
-		snprintf(buf, sizeof(buf)-1, "[%d] ", SDL_GetTicks() - start_time);
+		char buf[24];
+		snprintf(buf, sizeof(buf)-1, "[%llu] ",
+				(unsigned long long)(SDL_GetTicks() - start_time));
 		log_write_raw(l_levels[level].target, buf);
 	}
 }