Add exact arithmetic implementation and tests

- Introduced exact arithmetic with support for large integers and fractions in `exact.gd`, `big_integer.gd`, and `exact_value.gd`.
- Implemented a comprehensive test suite in `test_exact_math.gd` to validate arithmetic operations against expected results.
- Added a README in `math` directory to document the exact arithmetic system and its usage.
- Ensured that all arithmetic operations maintain precision without floating-point errors, using a custom representation for large numbers.
- Included methods for encoding and decoding exact values for serialization.

autoload/global.gd

@@ -1,4 +1,5 @@
 extends Node
+const E = preload("res://world/owniverse/math/exact.gd")
 
 const SPEED_LIMIT: int = 6
 
@@ -57,37 +58,15 @@ func get_description(item_id: String, items: Array = []) -> String:
     return render_template(row, variables)
 
 
-func format_number(value: float, digits: int = 0) -> String:
-    if value == 0: return ""
-    # Keep ordinary quantities readable, grouping thousands with spaces.
-    # Scientific notation is reserved for values whose fixed form would be
-    # unwieldy in the UI.
-    if absf(value) < 1_000_000_000.0:
-        var fixed: String = "%.*f" % [digits, value]
-        var parts: PackedStringArray = fixed.split(".", true)
-        var integer: String = parts[0]
-        var sign_prefix: String = ""
-        if integer.begins_with("-") or integer.begins_with("+"):
-            sign_prefix = integer.left(1)
-            integer = integer.substr(1)
-        var grouped: String = ""
-        while integer.length() > 3:
-            grouped = " " + integer.right(3) + grouped
-            integer = integer.left(integer.length() - 3)
-        grouped = sign_prefix + integer + grouped
-        return grouped + ("." + parts[1] if parts.size() > 1 else "")
-
-    var exp_value = int(floor(log(abs(value)) / log(10.0)))
-    var mantissa = value / pow(10.0, exp_value)
-    
-    return "%.*f" % [digits, mantissa] + "E%+d" % exp_value
+func format_number(value, digits: int = 0) -> String:
+    return E.grouped(value, digits)
 
 
 func _ready() -> void:
     CivilizationRules.clear()
     for row: Dictionary in _read_from_csv("res://data/civilization_rules.txt").values():
         if not CivilizationRules.has(row.stage):
-            CivilizationRules[row.stage] = {"home": row.home, "span": float(row.span), "stars": float(row.stars), "ethics": {},
+            CivilizationRules[row.stage] = {"home": row.home, "span": E.of(row.span), "stars": E.of(row.stars), "ethics": {},
                 "colonizes": row.colonizes == "1", "fights": row.fights == "1", "diplomacy": row.diplomacy == "1", "worships": row.worships == "1"}
         CivilizationRules[row.stage].ethics[row.ethic] = row
     var stages: Array = CivilizationRules.keys()
@@ -107,6 +86,8 @@ func _ready() -> void:
     Templates["en"] = _read_from_csv("res://data/templates.en.txt")
     Templates["ru"] = _read_from_csv("res://data/templates.ru.txt")
     
+    #Templates = OwniverseTemplates.get_data()
+    
 
 func _read_from_csv(file_path: String) -> Dictionary:
     if not FileAccess.file_exists(file_path):