feat(tui): status debounce, scroll indicator, drawer label, card grouping

Status messages now use a sequence counter so rapid actions don't
cause premature clearing. Detail pane shows scroll position and
supports pgup/pgdown/g/G. Capture drawer border includes inline
label. Cards view groups by intent (pinned/grab/read/fill) with
gutter labels matching the stream view's date grouping pattern.

internal/tui/detail.go

@@ -62,6 +62,17 @@ func (d detailModel) update(msg tea.KeyMsg) (detailModel, tea.Cmd) {
 			}
 		case "down", "j":
 			d.scroll++
+		case "pgdown", "ctrl+d":
+			d.scroll += d.height
+		case "pgup", "ctrl+u":
+			d.scroll -= d.height
+			if d.scroll < 0 {
+				d.scroll = 0
+			}
+		case "home", "g":
+			d.scroll = 0
+		case "end", "G":
+			d.scroll = 1<<31 - 1
 		}
 		return d, nil
 	}
@@ -156,8 +167,24 @@ func (d detailModel) previewView(width int) string {
 	b.WriteString(idStyle.Render(meta))
 
 	lines := strings.Split(b.String(), "\n")
-	if d.scroll > 0 && d.scroll < len(lines) {
-		lines = lines[d.scroll:]
+	totalLines := len(lines)
+
+	maxScroll := totalLines - d.height
+	if maxScroll < 0 {
+		maxScroll = 0
+	}
+	scroll := d.scroll
+	if scroll > maxScroll {
+		scroll = maxScroll
+	}
+
+	if totalLines > d.height && d.height > 0 && len(lines) > 0 {
+		indicator := idStyle.Render(fmt.Sprintf(" %d/%d", scroll+1, totalLines))
+		lines[0] = lines[0] + indicator
+	}
+
+	if scroll > 0 && scroll < totalLines {
+		lines = lines[scroll:]
 	}
 	if d.height > 0 && len(lines) > d.height {
 		lines = lines[:d.height]