WVS map uses shared plot_value_map; big5 value axes bipolar

The WVS map's ~70 lines of pole-signpost/hull/textalloc rendering were a copy of
what plot_value_map now does -- call the shared renderer instead (WVS + instruments
one code path). big5 value-axis poles named at both ends (Reserved<->Exploratory,
Volatile<->Stable) so every value map reads as a bipolar contrast, not a unipolar
low<->high.

Co-Authored-By: Claudypoo <288921227+claudypoo@users.noreply.github.com>

src/tinymfv/value_axes.py

@@ -35,8 +35,10 @@ VALUE_AXES: dict[str, tuple] = {
         ("Liberty", "Authority", [("liberty", -1), ("authority", 1)]),
     ),
     "big5": (
-        ("low Plasticity", "Plasticity", [("extraversion", 1), ("openness", 1)]),
-        ("low Stability", "Stability",
+        # DeYoung's meta-traits are unipolar, but name BOTH ends so every axis reads as a contrast
+        # (like the others): low Plasticity = reserved/conventional; low Stability = volatile.
+        ("Reserved", "Exploratory", [("extraversion", 1), ("openness", 1)]),
+        ("Volatile", "Stable",
          [("agreeableness", 1), ("conscientiousness", 1), ("neuroticism", -1)]),
     ),
     "humor_styles": (