Track testers

gps --package $PKG testers get internal
gps --package $PKG testers get alpha
gps --package $PKG --json testers get beta

Update emails (comma-separated or as supported by the CLI flags):

gps --package $PKG testers update internal \
  --emails qa@company.com,dev@company.com \
  --confirm

MCP / ops: gps_get_testers, gps_update_testers.

Notes: