fix(tui): use panel width for table layout in split-pane mode

Table columns were computed from terminal width, causing row wrapping
when the monitors panel only gets 70% of the space. Introduced
contentWidth field set per-tab in viewDashboard. computeLayout,
isWide, and renderTable now use contentWidth for column visibility,
available space, and max table width calculations.

Columns gracefully hide (SSL, RETRIES, TYPE, UPTIME) when the panel
is narrower, matching the existing responsive breakpoint behavior.

internal/tui/table_helpers.go

@@ -13,7 +13,11 @@ const (
 )
 
 func (m Model) isWide() bool {
-	return m.termWidth >= wideBreakpoint
+	w := m.contentWidth
+	if w == 0 {
+		w = m.termWidth
+	}
+	return w >= wideBreakpoint
 }
 
 func (m Model) renderTable(headers []string, items int, buildRows func(start, end int) [][]string, colWidths []int, styleOverride StyleOverride) string {
@@ -35,7 +39,11 @@ func (m Model) renderTable(headers []string, items int, buildRows func(start, en
 	}
 	borderOverhead := 2 + len(colWidths) - 1
 	tableWidth := colTotal + borderOverhead
-	maxWidth := m.termWidth - chromePadH - 2
+	cw := m.contentWidth
+	if cw == 0 {
+		cw = m.termWidth
+	}
+	maxWidth := cw - chromePadH - 2
 	if tableWidth > maxWidth {
 		tableWidth = maxWidth
 	}