[ hopefully someone will replace this comment with information on the meaning and format of the stream data that the wubwikit returns when page names are terminated with the ".str" suffix.
Data is stored in the wikit database in stream format. It has no particular significance beyond that which jcw attributed to it in format.tcl (a component of wikit) as an intermediate form for storing partially decoded wikit text, and there was no real utility in providing it as an output format beyond (perhaps) some hypothetical future wikit-to-wikit transfer facility CMcC.