Assert dry-run install writes nothing under projectRoot too (cursor target writes there, not home). Rewrite the concurrent writeInstallState test with genuinely overlapping writers via async spawn plus done-file rendezvous, including a mid-flight read; sanitize rendezvous filenames for Windows.
Honor ECC_DRY_RUN=1 in install and repair arg parsing (previously only --dry-run flag worked, so ecc --dry-run install/repair silently performed real writes). Make writeInstallState atomic via writeFileAtomic (O_EXCL staging, fsync, cleanup on failure, atomic rename preserving previous state). Add writeInstallState failure/concurrency/symlink regression tests and disposable-home CLI dry-run regression tests for both global and subcommand forms.
haelyra