Fix append-file concatenating without a newline (#204)

src/skills.metta

@@ -41,12 +41,14 @@
           WRITE-FILE-SUCCESS))
 
 (= (append-file $file $str)
-   (progn (translatePredicate (exists_file $file))
-          (translatePredicate (open $file append $Out))
-          (translatePredicate (write $Out $str))
-          (translatePredicate (nl $Out)),
-          (translatePredicate (close $Out))
-          APPEND-FILE-SUCCESS))
+   (let $sep (line_separator $file)
+        (progn (translatePredicate (exists_file $file))
+               (translatePredicate (open $file append $Out))
+               (translatePredicate (write $Out $sep))
+               (translatePredicate (write $Out $str))
+               (translatePredicate (nl $Out))
+               (translatePredicate (close $Out))
+               APPEND-FILE-SUCCESS)))
 
 (= (tavily-search $query)
    (py-call (agentverse.tavily_search $query)))
@@ -57,7 +59,7 @@
 (= (websearch $msg)
    (py-call (websearch.search $msg)))
 
-!(import_prolog_functions_from_file (library OmegaClaw-Core ./src/skills.pl) (shell first_char gc read_file_tail))
+!(import_prolog_functions_from_file (library OmegaClaw-Core ./src/skills.pl) (shell first_char gc read_file_tail line_separator))
 
 (= (metta $str)
    (let $code (sread $str)

src/skills.pl

@@ -54,3 +54,13 @@
         ),
         close(In)
     ).
+
+%Newline needed to start a new line at the end of Path, empty if already at one:
+line_separator(Path, Sep) :-
+    (   exists_file(Path),
+        read_file_tail(Path, 1, Tail),
+        Tail \== "",
+        Tail \== "\n"
+    ->  Sep = "\n"
+    ;   Sep = ""
+    ).