Add unit tests for action value formatting and distribution

- Implemented a new test script `test_action_values.gd` to verify the precision of fractional action amounts and the distinctiveness of adjacent values.
- Added checks to ensure that action values are correctly formatted and that the distribution of actions preserves distinct requests.
- Included validation for rendered button labels to confirm they are distinguishable.

ui/actions/actions.gd

@@ -47,9 +47,21 @@ func _set_action_values(values: Array, displayed: Array) -> void:
     for ind in range(0, 5):
         action_values[ind] = values[ind]
         # Keep the original request for execution; show the exact planned output.
-        var text: String = Global.format_number(displayed[ind]) if displayed[ind] > 0 else ""
+        var text: String = _format_action_value(displayed[ind])
         if action_labels[ind].text != text:
             action_labels[ind].text = text
+
+
+func _format_action_value(value: float) -> String:
+    if value <= 0.0 or not is_finite(value):
+        return ""
+    if value >= 1.0:
+        return Global.format_number(value)
+    # Global's default is intended for object counts. Action values may be
+    # fractional, so retain enough precision to keep adjacent buttons distinct.
+    var exponent: int = int(floor(log(value) / log(10.0)))
+    var digits: int = clampi(-exponent + 1, 2, 6)
+    return Global.format_number(value, digits)
         
 
 func _on_action_button_pressed(button_id: int) -> void: