v1.4.0

Release 1.4.0

Four switchable UI styles with light and dark halves, each with its
own desktop host-list layout on top of the same underlying list
behaviour; the terminal colour-scheme swatch rendering bug is fixed
alongside it. Multi-select and a fleet-wide file push round out the
release: bounded concurrency, per-host pass/fail with its own
reason, and retry for just what failed.

1445 tests, analyzer clean.