feat(tui): compact log sidebar with severity icons

Replace full viewLogsTab with compact sidebar renderer for the 70/30
monitors split. Single-char severity icons (▼▲◆●·), truncated messages,
no header chrome. Renders directly from engine logs without viewport.

internal/tui/tab_logs_sidebar.go

@@ -0,0 +1,64 @@
+package tui
+
+import (
+	"fmt"
+	"strings"
+)
+
+func (m Model) renderCompactLogLine(line string, maxW int) string {
+	sev := classifyLog(line)
+
+	var tag string
+	switch sev {
+	case severityDown:
+		tag = m.st.dangerStyle.Render("▼")
+	case severityUp:
+		tag = m.st.specialStyle.Render("▲")
+	case severityWarn:
+		tag = m.st.warnStyle.Render("◆")
+	case severitySystem:
+		tag = m.st.titleStyle.Render("●")
+	default:
+		tag = m.st.subtleStyle.Render("·")
+	}
+
+	ts := ""
+	msg := line
+	if len(line) > 10 && line[0] == '[' {
+		if idx := strings.Index(line, "]"); idx > 0 && idx < 12 {
+			ts = line[1:idx]
+			msg = strings.TrimSpace(line[idx+1:])
+		}
+	}
+
+	msgW := maxW - 10
+	if msgW < 10 {
+		msgW = 10
+	}
+	msg = limitStr(msg, msgW)
+
+	if ts != "" {
+		return fmt.Sprintf(" %s %s %s", m.st.subtleStyle.Render(ts), tag, msg)
+	}
+	return fmt.Sprintf(" %s %s", tag, msg)
+}
+
+func (m Model) viewLogsSidebar(width int) string {
+	logs := m.engine.GetLogs()
+	if len(logs) == 0 {
+		return m.st.subtleStyle.Render("  No logs yet")
+	}
+
+	var lines []string
+	for _, line := range logs {
+		if strings.TrimSpace(line) == "" {
+			continue
+		}
+		if m.logFilterImportant && !isImportantLog(classifyLog(line)) {
+			continue
+		}
+		lines = append(lines, m.renderCompactLogLine(line, width))
+	}
+
+	return strings.Join(lines, "\n")
+}