Add omacalc v0.1.0

Includes the .omarchy/package.json metadata the release pipeline
requires to enumerate a package -- without it, bin/repo release
silently skips the directory.

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

pkgbuilds/omacalc/.omarchy/package.json

@@ -0,0 +1,3 @@
+{
+  "source": "local"
+}