The rail spent a two-row block plus a divider on per-user sync status. It's
global, not per-module, so it now rides the right end of the floating header as
a pill: the headline count at a glance, an accent dot when something wants you
(paused / missing history), and the counts, state, the channel-manager link and
pause in a popover.
Frees the rail's whole top block. Also drops SyncStatus's two now-dead layouts:
"bar" was a leftover of the top bar removed in 0.42.0, and "rail" lost its only
caller here — the component is chip-only, ~60 lines lighter, and the popover
reuses useDismiss.
peter
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