Initial import of LogDarioSeq baseline

Establishes version control for the personal Logseq DB fork before
starting the server-client architecture migration and domain features
described in docs/agent-guide and the approved implementation plan.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

cli/spec/core/ustring.mli

@@ -0,0 +1,8 @@
+type t = private string
+(** unicode string *)
+
+val of_string : string -> t
+(** convert utf8-encoded byte string to unicode string *)
+
+val to_string : t -> string
+(** identity *)