build: pin the @sorb scope to rohana instead of relying on the lockfile

Nothing in this repo said where @sorb/threadnet-call-embedded comes from. It
worked only because pnpm-lock.yaml carries the full tarball URL and CI installs
with --frozen-lockfile; the first version bump drops that cover. Today that ends
in a 404 because the name is still free on npmjs - which makes our only
protection the fact that nobody has claimed @sorb there. Claim it and the same
command resolves silently against a stranger's package, in the exact moment a
fresh download looks normal.

The checked-in .npmrc closes the wrong path instead of documenting it. It holds a
URL and no secret: read access to the registry is anonymous.

Upstream's .gitignore ignores /.npmrc - reasonable where the file holds tokens,
and it would have swallowed this fix without a word. The negation is explicit and
carries the reason, so the next merge does not quietly restore the hole.

Verified in an isolated tree, not assumed: without the file pnpm resolves to
npmjs and fails; with it the scope resolves to rohana at the same integrity hash
the repo lockfile already carries; with rohana unreachable the install fails
outright rather than falling back to npmjs. pnpm install --frozen-lockfile still
passes and leaves the lockfile untouched.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.npmrc

@@ -0,0 +1,15 @@
+# Der Scope @sorb liegt in der Gitea-Registry auf rohana, nicht auf npmjs.
+#
+# Ohne diese Zeile loest pnpm @sorb/threadnet-call-embedded gegen
+# registry.npmjs.org auf. Dass das bisher gutging, lag allein am Lockfile: es
+# pinnt die vollstaendige Tarball-URL, und die CI installiert mit
+# --frozen-lockfile. Beim ersten Anheben der Version faellt dieser Schutz weg.
+#
+# Heute endet das in einem 404, weil der Name auf npmjs frei ist. Genau darauf
+# darf man sich nicht verlassen: registriert dort jemand @sorb, loest derselbe
+# Befehl still gegen ein fremdes Paket auf (dependency confusion) - und zwar in
+# dem Moment, in dem ein neuer Download ohnehin erwartet wird.
+#
+# Kein Geheimnis in dieser Datei: der Lesezugriff auf die Registry ist anonym.
+# Siehe management#0055.
+@sorb:registry=https://rohana.axion1337.de/api/packages/sorb/npm/