Replace temp .npmrc + --userconfig approach with the --@mosaic:registry CLI
flag so the user's real ~/.npmrc (including prefix=/home/user/.npm-global)
is honoured. This eliminates EACCES errors for non-root installs that
relied on a user-level prefix config.
Bump @mosaic/cli and @mosaic/mosaic to 0.0.15.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>