refactor: pre-format numbers for sphere attribute tooltips

This results in an uneven presentation when floating point numbers are
displayed, but avoids e.g. caster level parts from classes with lower
progressions being rounded up in the display, leading to confusing and
incorrect sources.

src/module/sphere-tooltip.ts

@@ -187,7 +187,7 @@ const getSources = (
     .filter((source) => !source.modifier)
     .map((source) => ({
       ...source,
-      value: source.value ?? 0,
+      value: formatValue(source.value),
       type:
         pf1.config.bonusTypes[(source.type as BonusType) || (source.modifier as BonusType)] ||
         pf1.config.bonusTypes.untyped,
@@ -197,20 +197,46 @@ const getSources = (
     .filter((source) => source.modifier)
     .map((source) => ({
       ...source,
-      value: source.value ?? 0,
+      value: formatValue(source.value),
       type: pf1.config.bonusTypes[(source.type as BonusType) || (source.modifier as BonusType)],
     }));
   const capped = (actor.sourceDetails[modCapPath] ?? [])
     .filter(filterDummySources)
-    .map((source) => ({ ...source, value: source.value ?? 0, type: localize("CappedByHD") }));
+    .map((source) => ({
+      ...source,
+      value: formatValue(source.value),
+      type: localize("CappedByHD"),
+    }));
   return { base, bonus, capped };
 };
 
+/**
+ * Filter out sources taken from another source (e.g. base CL to sphere CL), implied by the name being the bonus type.
+ *
+ * @param source - The source to filter
+ */
 const filterDummySources = (source: SourceEntry): boolean => {
   if (source.name in CONFIG.PF1.bonusTypes) return false;
   return true;
 };
 
+/**
+ * Format a number value to be suitable for tooltip display.
+ * If the value is a floating point number, it is formatted to one decimal place and returned as string;
+ * this results in the tooltip display becoming uneven, but is necessary to display e.g. correct partial caster level parts.
+ *
+ * @param value - The value to format
+ * @param options - Formatting options
+ * @param options.sign - Whether to include a sign for positive values
+ */
+const formatValue = (value = 0, { sign = true } = {}): number | string => {
+  const isFloat = value % 1 !== 0;
+  if (!isFloat) return value;
+  const fixed = parseFloat(`${value}`).toFixed(1);
+  if (sign) return value >= 0 ? `+${fixed}` : fixed;
+  return fixed;
+};
+
 type SphereTooltipId =
   | "cl"
   | "msb"