SysMon 2.2.1

Upgrade-day fix: a plain sysmon launch used to raise whatever GUI was
already running — install a new version with the old window up and you
keep looking at the old UI. Now the new binary compares versions over the
control socket: a same-version instance is raised as before; an older
instance is asked to quit and replaced, with a console line saying so.
Installing a release and relaunching now always shows the version you
installed.

Also: the README was tightened into a single evergreen description
(feature history lives here in the release notes, not on the front page).

No other behavior changes. 42 tests green, full e2e pass, live takeover
receipt: a running 2.2.0 was replaced by this binary during verification.