🚨 Silence helper oxlint warnings

The completion helper is test-only (excluded from dist/), so the
style-only no-magic-numbers and unicorn/no-null warnings are tolerable
here. A file-level disable keeps them out of check:oxlint without touching
the project config.

src/util/__tests__/lsp-completion.ts

@@ -1,3 +1,4 @@
+// oxlint-disable no-magic-numbers unicorn/no-null - tolerable here, this is a helper
 import { spawn, type ChildProcessWithoutNullStreams } from "node:child_process";
 import fs from "node:fs";
 import path from "node:path";