Two review findings. Chromium 96 moved the cookie database to
`Network/Cookies`, but the reader only ever looked at `{profile}/Cookies` —
so an install carrying a leftover root jar imported a stale or empty
database while the real sessions lived under `Network/`, and a fresh install
with only the `Network/` jar read as not installed and was hidden. Discovery,
counts, the installed check and the importer now resolve the first candidate
that is a regular file, most-current first.

And a second Import click before React left the configure screen started a
second run; the parent refused it, and the wizard applied that refusal as a
read failure — dropping out of the importing step mid-write and showing a
false error over a successful import. A synchronous in-flight ref now makes
the second click a no-op.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>