Group rows now show selection background when navigated to. Layout
chrome extracted to named constants to prevent viewport drift. Groups
display aggregate history as dot sparkline (●) distinct from site
bar sparklines, with uptime computed from active children only.
Paused and maintenance children excluded from group aggregates.
- New table_helpers.go with renderTable() and shared styles
- Remove 4 duplicated style blocks (header/cell/selected/border)
from tab_alerts.go and tab_users.go
- All 3 tab views now use renderTable() for offset/end calc,
selected row highlighting, and table construction
- Sites tab keeps siteGroupStyle via StyleOverride callback
- Clamp cursor to list length at end of refreshData() to prevent
index-out-of-bounds after concurrent list changes
- Fix off-by-one in tab click handler (i <= maxTabs → i < tabCount)
lerko