gitnexus-shared was declared as a file: dependency but never published
to npm, causing ERR_MODULE_NOT_FOUND for users installing gitnexus
globally. The build script now copies gitnexus-shared/dist into
dist/_shared/ and rewrites bare specifiers to relative paths.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>