feat(tui): stable detail panel height with scroll support

Detail sidebar now maintains consistent height matching the monitors
panel across all modes (default, SLA, history). Content scrolls within
the fixed frame via mouse wheel or j/k when the detail panel is
focused. Scroll offset resets on mode/monitor/period changes. Logs
strip stays visible in all states.

internal/tui/update.go

@@ -298,6 +298,18 @@ func (m *Model) handleMouse(msg tea.MouseMsg) (tea.Model, tea.Cmd) {
 		return m, nil
 	}
 
+	if m.focusedPanel == panelDetail && m.detailOpen {
+		if msg.Button == tea.MouseButtonWheelUp {
+			m.detailScrollOffset -= 3
+		} else {
+			m.detailScrollOffset += 3
+		}
+		if m.detailScrollOffset < 0 {
+			m.detailScrollOffset = 0
+		}
+		return m, nil
+	}
+
 	listLen := m.currentListLen()
 	if msg.Button == tea.MouseButtonWheelUp {
 		if m.cursor > 0 {
@@ -588,6 +600,13 @@ func (m *Model) handleDashboardKey(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 		}
 		m.recalcLayout()
 	case "up", "k":
+		if m.focusedPanel == panelDetail && m.detailOpen {
+			m.detailScrollOffset--
+			if m.detailScrollOffset < 0 {
+				m.detailScrollOffset = 0
+			}
+			return m, nil
+		}
 		if m.focusedPanel == panelMaint {
 			m.scrollMaintCursor(-1)
 			return m, nil
@@ -604,10 +623,15 @@ func (m *Model) handleDashboardKey(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 			m.syncSelectedID()
 			if m.detailOpen && m.cursor < len(m.sites) {
 				m.detailMode = detailDefault
+				m.detailScrollOffset = 0
 				return m, m.loadDetailCmd(m.sites[m.cursor].ID)
 			}
 		}
 	case "down", "j":
+		if m.focusedPanel == panelDetail && m.detailOpen {
+			m.detailScrollOffset++
+			return m, nil
+		}
 		if m.focusedPanel == panelMaint {
 			m.scrollMaintCursor(1)
 			return m, nil
@@ -625,6 +649,7 @@ func (m *Model) handleDashboardKey(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 			m.syncSelectedID()
 			if m.detailOpen && m.cursor < len(m.sites) {
 				m.detailMode = detailDefault
+				m.detailScrollOffset = 0
 				return m, m.loadDetailCmd(m.sites[m.cursor].ID)
 			}
 		}
@@ -652,6 +677,7 @@ func (m *Model) handleDashboardKey(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 		if len(m.sites) > 0 {
 			m.detailOpen = !m.detailOpen
 			m.detailMode = detailDefault
+			m.detailScrollOffset = 0
 			m.recalcLayout()
 			st := m.store
 			ctx := m.ctx
@@ -702,9 +728,11 @@ func (m *Model) handleDashboardKey(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 			m.focusedPanel = panelMonitors
 		} else if m.detailOpen && m.detailMode != detailDefault {
 			m.detailMode = detailDefault
+			m.detailScrollOffset = 0
 		} else if m.detailOpen {
 			m.detailOpen = false
 			m.detailMode = detailDefault
+			m.detailScrollOffset = 0
 			m.recalcLayout()
 			st := m.store
 			ctx := m.ctx
@@ -719,6 +747,7 @@ func (m *Model) handleDashboardKey(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 			m.historySiteID = site.ID
 			m.historyChanges = nil
 			m.detailMode = detailHistory
+			m.detailScrollOffset = 0
 			return m, m.loadHistoryCmd(site.ID)
 		}
 	case "s":
@@ -728,6 +757,7 @@ func (m *Model) handleDashboardKey(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 			m.slaSiteID = site.ID
 			m.slaPeriodIdx = 2
 			m.detailMode = detailSLA
+			m.detailScrollOffset = 0
 			return m, m.loadSLACmd(site.ID, m.slaPeriodIdx)
 		}
 	case "1", "2", "3", "4":
@@ -735,6 +765,7 @@ func (m *Model) handleDashboardKey(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
 			idx := int(msg.String()[0]-'0') - 1
 			if idx >= 0 && idx < len(slaPeriods) {
 				m.slaPeriodIdx = idx
+				m.detailScrollOffset = 0
 				return m, m.loadSLACmd(m.slaSiteID, idx)
 			}
 		}
@@ -860,6 +891,7 @@ func (m *Model) handleClick(msg tea.MouseMsg) (tea.Model, tea.Cmd) {
 			m.syncSelectedID()
 			m.focusedPanel = panelMonitors
 			if m.detailOpen {
+				m.detailScrollOffset = 0
 				return m, m.loadDetailCmd(m.sites[m.cursor].ID)
 			}
 			return m, nil