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/lib/ustring.ml

@@ -0,0 +1,38 @@
+type t = string
+type uint8_array
+type text_decoder
+
+external char_code_at : string -> int -> int = "charCodeAt" [@@mel.send]
+external uint8_array_from : string -> (string -> int) -> uint8_array = "from"
+[@@mel.scope "Uint8Array"]
+
+external make_text_decoder : string -> < fatal : bool > Js.t -> text_decoder
+  = "TextDecoder"
+[@@mel.new]
+
+external decode : text_decoder -> uint8_array -> string = "decode" [@@mel.send]
+
+type string_kind = Ascii | Utf8_bytes | Unicode
+
+let decoder = make_text_decoder "utf-8" [%obj { fatal = true }]
+
+let string_kind value =
+  let length = String.length value in
+  let rec loop index =
+    if index >= length then Ascii
+    else
+      let code = char_code_at value index in
+      if code > 0xff then Unicode
+      else if code > 0x7f then Utf8_bytes
+      else loop (index + 1)
+  in
+  loop 0
+
+let of_string value =
+  match string_kind value with
+  | Ascii | Unicode -> value
+  | Utf8_bytes ->
+      let payload = uint8_array_from value (fun ch -> char_code_at ch 0) in
+      (try decode decoder payload with _ -> value)
+
+let to_string value = value