fix(resolve): unbreak the build — narrow parseRegistryName's destructured parts

CI has been red on main since #48: noUncheckedIndexedAccess types the
destructured `label`/`tld` as `string | undefined`, because TS can't narrow an
array to a 2-tuple from a `parts.length !== 2` check. Four TS2345/TS2322
errors failed `apps/desktop` and took the whole `pnpm -r build` with it.

Guard explicitly. Behavior is unchanged: length 2 already guarantees both
values, and an empty label would fail LABEL.test() on the next line anyway.

Unrelated to this branch's auth work, but it blocks the PR from going green.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: ralyodio

apps/desktop/src/moshpit-resolve.ts

@@ -112,6 +112,11 @@ export function parseRegistryName(hostname: string): { label: string; tld: strin
   const parts = host.split('.');
   if (parts.length !== 2) return null;
   const [label, tld] = parts;
+  // `parts.length !== 2` above already guarantees both exist, but
+  // noUncheckedIndexedAccess types them as `string | undefined` — TS can't
+  // narrow an array to a 2-tuple from a length check. An empty label would
+  // fail LABEL.test() anyway, so this guard changes no behavior.
+  if (!label || !tld) return null;
   const LABEL = /^[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?$/;
   if (!LABEL.test(label) || !LABEL.test(tld)) return null;
   return { label, tld };