Add collection and sorting utilities with Gitea release workflows

Replace retrocycle eval calls with property traversal and regression coverage. Add bundle budgets, eval guards, package publishing, and contributor documentation.

src/collections/index.ts

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+/** Group items by key, preserving item and first-seen key order. */
+export function groupBy<T, K>(items: readonly T[], keyOf: (item: T) => K): Map<K, T[]> {
+  const groups = new Map<K, T[]>();
+  for (const item of items) {
+    const key = keyOf(item);
+    const group = groups.get(key);
+    if (group) group.push(item);
+    else groups.set(key, [item]);
+  }
+  return groups;
+}
+
+/** Index items by key. The last item wins for duplicate keys. */
+export function keyBy<T, K>(items: readonly T[], keyOf: (item: T) => K): Map<K, T> {
+  const result = new Map<K, T>();
+  for (const item of items) result.set(keyOf(item), item);
+  return result;
+}
+
+/** Keep the first item for each key, preserving input order. */
+export function uniqueBy<T, K>(items: readonly T[], keyOf: (item: T) => K): T[] {
+  const seen = new Set<K>();
+  return items.filter(item => {
+    const key = keyOf(item);
+    if (seen.has(key)) return false;
+    seen.add(key);
+    return true;
+  });
+}
+
+/** Split items into [matching, non-matching], preserving order. */
+export function partition<T>(items: readonly T[], predicate: (item: T) => boolean): [T[], T[]] {
+  const matching: T[] = [];
+  const remaining: T[] = [];
+  for (const item of items) (predicate(item) ? matching : remaining).push(item);
+  return [matching, remaining];
+}