routie dev init since i didn't adhere to any proper guidance up until now

frontend/node_modules/eslint-plugin-perfectionist/dist/utils/pairwise.js

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+/**
+ * Iterates through an array calling a callback for each adjacent pair.
+ *
+ * Processes elements in pairs where:
+ *
+ * - First call: left is null, right is the first element
+ * - Subsequent calls: left and right are adjacent elements.
+ *
+ * This pattern is particularly useful for comparing adjacent elements in
+ * sorting validation, where each element needs to be compared with its
+ * predecessor to ensure correct ordering.
+ *
+ * @example
+ *
+ * ```ts
+ * // Common use case: checking sort order
+ * const numbers = [1, 3, 2, 4]
+ * const errors: string[] = []
+ *
+ * pairwise(numbers, (left, right) => {
+ *   if (left !== null && left > right) {
+ *     errors.push(`${left} should come after ${right}`)
+ *   }
+ * })
+ * // errors = ['3 should come after 2']
+ * ```
+ *
+ * @template T - Type of array elements.
+ * @param nodes - Array to iterate through.
+ * @param callback - Function called for each pair (including null for first).
+ */
+function pairwise(nodes, callback) {
+  if (nodes.length === 0) {
+    return
+  }
+  callback(null, nodes.at(0))
+  for (let i = 1; i < nodes.length; i++) {
+    callback(nodes.at(i - 1), nodes.at(i))
+  }
+}
+export { pairwise }