feat: show sync report for manual :DooingSync even when routine

fix: replace broken ETag concurrency with version-based checks

fix: make sync lock non-blocking and sandbox integration tests

feat: async startup sync and configurable exit sync, skip headless

feat: add concurrency protection with local locking and ETag-based conditional push

fix: eliminate false change notifications from vim.NIL and non-deterministic JSON serialization

feat: add configurable notification verbosity

Update repo path in README

Google Drive sync companion plugin for dooing.nvim.