sshkeeper v0.8.1 — Windows workspace input fixes

v0.8.1 fixes two input regressions found during the first native-Windows test of
the v0.8 Session Workspace.

Fixed

Mouse clicks now select the row actually clicked. The dashboard header is
two terminal rows (title plus separator), but v0.8.0 mouse hit-testing counted
it as one. On the server list this selected the next visible row, e.g. clicking
kp_gate selected KP_Mail.
Reliable workspace cycling on native Windows. Bubble Tea 1.3.x discards
the Ctrl modifier from native Windows PageUp/PageDown console events, so
Ctrl+PgUp / Ctrl+PgDn cannot be distinguished there. SSHKeeper now also
supports Alt+Left / Alt+Right for previous/next workspace tab. The
original Ctrl+PageUp/PageDown shortcuts remain available on terminals that
report them correctly.

Regression tests cover grouped server-list mouse coordinates and the new
workspace cycle shortcut.