refactor(tui): two-tier responsive table layout (compact/wide at 120 cols)

Replace continuous surplus distribution with two fixed layouts per table.
Breakpoint at 120 columns — matches how btop/k9s do it.

Compact (<120): short headers (LAT, UP%, RT, ST, MON, SENT, VER),
  tight fixed widths, no surplus guessing.

Wide (≥120): full headers (LATENCY, UPTIME, RETRIES, STATUS, MONITORS,
  LAST SENT, VERSION), generous widths.

Sites tab keeps content-aware NAME sizing + sparkline flex.
All other tabs (Alerts, Maint, Nodes, Users) use simple fixed tiers.

Removed old computeTableLayout/colDef/tierCol/pickTier — no longer needed.

internal/tui/table_helpers.go

@@ -15,77 +15,10 @@ var (
 
 type StyleOverride func(row, col int) *lipgloss.Style
 
-type colDef struct {
-	short    string
-	full     string
-	minWidth int
-	maxWidth int
-	flex     bool
-}
+const wideBreakpoint = 120
 
-func (m Model) computeTableLayout(cols []colDef, maxContentWidth int) ([]string, []int) {
-	numCols := len(cols)
-	borderOverhead := 2 + (numCols - 1)
-	usable := m.termWidth - chromePadH - 2 - borderOverhead
-	if usable < 40 {
-		usable = 40
-	}
-
-	fixedMin := 0
-	flexIdx := -1
-	for i, c := range cols {
-		if c.flex {
-			flexIdx = i
-			continue
-		}
-		fixedMin += c.minWidth
-	}
-
-	flexW := usable - fixedMin
-	if maxContentWidth > 0 && flexW > maxContentWidth {
-		flexW = maxContentWidth
-	}
-	if flexW < 8 {
-		flexW = 8
-	}
-
-	surplus := usable - fixedMin - flexW
-	if surplus < 0 {
-		surplus = 0
-	}
-
-	headers := make([]string, numCols)
-	widths := make([]int, numCols)
-	for i, c := range cols {
-		if c.flex {
-			headers[i] = c.full
-			widths[i] = flexW
-			continue
-		}
-
-		w := c.minWidth
-		expand := c.maxWidth - c.minWidth
-		if surplus >= expand {
-			w = c.maxWidth
-			surplus -= expand
-		} else if surplus > 0 {
-			w += surplus
-			surplus = 0
-		}
-
-		if w >= len(c.full)+2 {
-			headers[i] = c.full
-		} else {
-			headers[i] = c.short
-		}
-		widths[i] = w
-	}
-
-	if surplus > 0 && flexIdx >= 0 {
-		widths[flexIdx] += surplus
-	}
-
-	return headers, widths
+func (m Model) isWide() bool {
+	return m.termWidth >= wideBreakpoint
 }
 
 func (m Model) renderTable(headers []string, items int, buildRows func(start, end int) [][]string, colWidths []int, styleOverride StyleOverride) string {