Document the sort array function

`sort` was implemented, registered, and tested, but had no entry in the
language-service docs registry and was missing from the quick reference.

- Add a `sort` entry to `BUILTIN_FUNCTION_DOCS` so IDE/playground hover and
  completions show its description and `a` / `f` (optional comparator) params.
- Add a `sort` row to the Array Functions table in `docs/quick-reference.md`.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: Sander Toonen

docs/quick-reference.md

@@ -86,6 +86,7 @@ This is a quick reference card. For detailed documentation, see [Expression Synt
 | `indexOf(arr, val)` | `indexOf([1, 2, 3], 2)` | 1 |
 | `join(arr, sep)` | `join([1, 2], "-")` | "1-2" |
 | `unique(arr)` | `unique([1, 1, 2])` | [1, 2] |
+| `sort(arr, fn?)` | `sort([3, 1, 2])` | [1, 2, 3] |
 | `map(arr, fn)` | `map([1, 2], x => x * 2)` | [2, 4] |
 | `filter(arr, fn)` | `filter([1, 2, 3], x => x > 1)` | [2, 3] |
 | `find(arr, fn)` | `find([1, 5, 2], x => x > 3)` | 5 |

packages/expreszo/src/registry/builtin/function-docs.ts

@@ -394,6 +394,17 @@ export const BUILTIN_FUNCTION_DOCS: Readonly<Record<string, FunctionDocs>> = {
       { name: 'size', description: 'Positive integer chunk size.', type: 'number' }
     ]
   },
+  sort: {
+    description:
+      'Return a sorted copy of an array (the original is not mutated). With no comparator, ' +
+      'values are sorted in natural ascending order. Optionally pass a comparator f(a, b) ' +
+      'that returns a negative number, zero, or a positive number to order a before, equal ' +
+      'to, or after b.',
+    params: [
+      { name: 'a', description: 'Input array.', type: 'array' },
+      { name: 'f', description: 'Optional comparator (a, b) => number.', optional: true, type: 'function' }
+    ]
+  },
   union: {
     description: 'Concatenate arrays and remove duplicates, preserving first-seen order. Element equality follows Set semantics (strict for primitives, reference for objects).',
     params: [