convert all eval visualization paths to incrementally building expression trees, rather than using final eval bundles; ensure all evaluation paths, in various circumstances (single line viz, row viz), go through exactly the same path; deduplicate single-row-expr evaluation paths

src/eval/eval_core.h

@@ -36,6 +36,27 @@ struct E_MsgList
   U64 count;
 };
 
+////////////////////////////////
+//~ rjf: Operator Info
+
+typedef enum E_OpKind
+{
+  E_OpKind_Null,
+  E_OpKind_UnaryPrefix,
+  E_OpKind_Binary,
+}
+E_OpKind;
+
+typedef struct E_OpInfo E_OpInfo;
+struct E_OpInfo
+{
+  E_OpKind kind;
+  S64 precedence;
+  String8 pre;
+  String8 sep;
+  String8 post;
+};
+
 ////////////////////////////////
 //~ rjf: Evaluation Spaces