feat(vue): expand @robonen/vue composable collection

Composables, tests, category barrels, and README for @robonen/vue.

vue/toolkit/src/composables/math/useAverage/index.ts

@@ -0,0 +1,55 @@
+import { isArray, sum } from '@robonen/stdlib';
+import { computed, toValue } from 'vue';
+import type { ComputedRef, MaybeRefOrGetter } from 'vue';
+import type { MaybeComputedRefArgs } from '@/types';
+
+/**
+ * @name useAverage
+ * @category Math
+ * @description Reactively compute the average (arithmetic mean) of the provided
+ * numbers. Accepts either a variadic list of numbers (each a ref, getter, or raw
+ * value) or a single reactive array whose items may themselves be refs/getters.
+ * Returns `NaN` when there are no values, mirroring `0 / 0`.
+ *
+ * @param {...MaybeRefOrGetter<number>} args The values to average, or a single reactive array of values
+ * @returns {ComputedRef<number>} A computed ref of the mean (`NaN` when empty)
+ *
+ * @example
+ * const a = ref(1);
+ * const b = ref(3);
+ * const avg = useAverage(a, b, 2); // 2
+ *
+ * @example
+ * const list = ref([1, 5, 3]);
+ * const avg = useAverage(list); // 3
+ *
+ * @example
+ * const list = ref([ref(2), () => 4, 6]);
+ * const avg = useAverage(list); // 4
+ *
+ * @since 0.0.15
+ */
+export function useAverage(array: MaybeRefOrGetter<Array<MaybeRefOrGetter<number>>>): ComputedRef<number>;
+export function useAverage(...args: Array<MaybeRefOrGetter<number>>): ComputedRef<number>;
+export function useAverage(...args: MaybeComputedRefArgs<number>): ComputedRef<number> {
+  return computed<number>(() => {
+    // Collect into a single flat numeric array so we can reuse stdlib `sum`
+    // and divide by the real count in one pass — no intermediate flatMap.
+    const values: number[] = [];
+
+    for (const arg of args) {
+      const value = toValue(arg);
+
+      if (isArray(value)) {
+        for (const inner of value)
+          values.push(toValue(inner));
+      }
+      else {
+        values.push(value);
+      }
+    }
+
+    // Empty -> NaN (0 / 0), matching the mathematical definition of a mean.
+    return sum(values) / values.length;
+  });
+}