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/tab_sites.go

@@ -341,31 +341,29 @@ type tableLayout struct {
 }
 
 func (m Model) computeLayout() tableLayout {
-	cols := []colDef{
-		{"#", "#", 4, 4, false},
-		{"", "", 0, 0, false}, // NAME (special)
-		{"TYPE", "TYPE", 8, 10, false},
-		{"STATUS", "STATUS", 8, 10, false},
-		{"LAT", "LATENCY", 7, 10, false},
-		{"UP%", "UPTIME", 8, 8, false},
-		{"", "", 0, 0, false}, // HISTORY (special)
-		{"SSL", "SSL", 5, 5, false},
-		{"RT", "RETRIES", 5, 9, false},
+	wide := m.isWide()
+
+	var fixed int
+	var headers []string
+	var widths []int
+
+	if wide {
+		//              #   NAME TYPE   STATUS LATENCY UPTIME HISTORY SSL RETRIES
+		headers = []string{"#", "NAME", "TYPE", "STATUS", "LATENCY", "UPTIME", "HISTORY", "SSL", "RETRIES"}
+		widths = []int{4, 0, 10, 10, 10, 8, 0, 7, 9}
+		fixed = 4 + 10 + 10 + 10 + 8 + 7 + 9
+	} else {
+		//              #   NAME TYPE   STATUS LAT   UP%   HISTORY SSL RT
+		headers = []string{"#", "NAME", "TYPE", "STATUS", "LAT", "UP%", "HISTORY", "SSL", "RT"}
+		widths = []int{4, 0, 8, 8, 7, 7, 0, 5, 5}
+		fixed = 4 + 8 + 8 + 7 + 7 + 5 + 5
 	}
 
-	numCols := len(cols)
-	borderOverhead := 2 + (numCols - 1) // left + right border + column separators
-	usable := m.termWidth - chromePadH - 2 - borderOverhead
-	if usable < 80 {
-		usable = 80
-	}
-
-	fixedMin := 0
-	for i, c := range cols {
-		if i == 1 || i == 6 {
-			continue
-		}
-		fixedMin += c.minWidth
+	numCols := len(headers)
+	borderOverhead := 2 + (numCols - 1)
+	avail := m.termWidth - chromePadH - 2 - borderOverhead - fixed
+	if avail < 20 {
+		avail = 20
 	}
 
 	maxName := 0
@@ -374,68 +372,26 @@ func (m Model) computeLayout() tableLayout {
 			maxName = n
 		}
 	}
-	maxName += 4 // icon + padding + error preview room
+	maxName += 4
 
-	avail := usable - fixedMin
 	nameW := avail / 2
 	if nameW > maxName {
 		nameW = maxName
 	}
-	sparkW := avail - nameW - 2
-
 	if nameW < 13 {
 		nameW = 13
 	}
 	if nameW > 40 {
 		nameW = 40
 	}
+
+	sparkW := avail - nameW
 	if sparkW < 10 {
 		sparkW = 10
 	}
-	if sparkW > 60 {
-		sparkW = 60
-	}
 
-	surplus := usable - fixedMin - nameW - sparkW - 2
-	if surplus < 0 {
-		surplus = 0
-	}
-
-	headers := make([]string, len(cols))
-	widths := make([]int, len(cols))
-	for i, c := range cols {
-		if i == 1 {
-			headers[i] = "NAME"
-			widths[i] = nameW
-			continue
-		}
-		if i == 6 {
-			headers[i] = "HISTORY"
-			widths[i] = sparkW + 2
-			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 {
-		widths[6] += surplus
-	}
+	widths[1] = nameW
+	widths[6] = sparkW
 
 	return tableLayout{
 		nameW:     nameW,