feat(tui): add split-pane detail, compact date headers, and input drawer

Three layout improvements for better space utilization:

- Compact date headers: date labels render as left gutter column instead
  of standalone lines, saving one line per date group in stream view
- Input drawer: capture bar expands to 4-line drawer with border, hints,
  and live preview of parsed entity/search query
- Split-pane detail: wide terminals (>=100 cols) show list and detail
  side-by-side with h/l focus switching, falling back to full-screen
  detail on narrow terminals

internal/tui/styles.go

@@ -105,4 +105,21 @@ var (
 	searchPillStyle = lipgloss.NewStyle().
 			Foreground(lipgloss.AdaptiveColor{Light: "#E06C75", Dark: "#E06C75"}).
 			Bold(true)
+
+	gutterStyle = lipgloss.NewStyle().
+			Foreground(dim)
+
+	drawerBorderStyle = lipgloss.NewStyle().
+				Foreground(dim)
+
+	drawerHintsStyle = lipgloss.NewStyle().
+				Foreground(dim).
+				PaddingLeft(2)
+
+	drawerPreviewStyle = lipgloss.NewStyle().
+				Foreground(lipgloss.AdaptiveColor{Light: "#555555", Dark: "#AAAAAA"}).
+				PaddingLeft(2)
+
+	separatorStyle = lipgloss.NewStyle().
+			Foreground(dim)
 )