feat(office): mail preview, infinite scroll, pane resize, and scrollbars

Polish the office TUI with proportional pane layout, drag resize, live
filtering, HTML mail preview, paginated mail lists, overflow scrollbars,
flattened navigation, and project save/status fixes; add UpdateProjectStatus.

Co-authored-by: Cursor <cursoragent@cursor.com>

cmd/office/ui/layout.go

@@ -17,44 +17,60 @@ func defaultPaneVisibility() PaneVisibility {
 	return PaneVisibility{Menu: true, List: true, Detail: true}
 }
 
-// LayoutWidths splits total terminal width evenly across visible panes.
+const (
+	defaultMenuShare  = 10
+	defaultListShare  = 60
+	defaultDetailShare = 30
+)
+
+// LayoutWidths splits total terminal width across visible panes (default 10% / 60% / 30%).
 func LayoutWidths(total int, vis PaneVisibility) PaneWidths {
 	if total < 1 {
 		total = 80
 	}
 	v := vis
-	n := countVisible(v)
-	if n == 0 {
+	if countVisible(v) == 0 {
 		v = defaultPaneVisibility()
-		n = 3
 	}
-	base := total / n
-	rem := total % n
-	out := PaneWidths{Visibility: v}
+	shareSum := 0
 	if v.Menu {
-		out.Menu = base
-		if rem > 0 {
-			out.Menu++
-			rem--
-		}
+		shareSum += defaultMenuShare
 	}
 	if v.List {
-		out.List = base
-		if rem > 0 {
-			out.List++
-			rem--
-		}
+		shareSum += defaultListShare
 	}
 	if v.Detail {
-		out.Detail = base
-		if rem > 0 {
-			out.Detail++
-			rem--
-		}
+		shareSum += defaultDetailShare
 	}
+	assign := func(visible bool, share int) int {
+		if !visible || shareSum == 0 {
+			return 0
+		}
+		return total * share / shareSum
+	}
+	out := PaneWidths{Visibility: v}
+	out.Menu = assign(v.Menu, defaultMenuShare)
+	out.List = assign(v.List, defaultListShare)
+	out.Detail = assign(v.Detail, defaultDetailShare)
+	fixPaneWidthSum(&out, total)
 	return out
 }
 
+// DetailPaneXRange returns the [start, end) column span of the detail pane.
+func DetailPaneXRange(pw PaneWidths) (start, end int) {
+	if !pw.Visibility.Detail {
+		return 0, 0
+	}
+	if pw.Visibility.Menu {
+		start += pw.Menu
+	}
+	if pw.Visibility.List {
+		start += pw.List
+	}
+	end = start + pw.Detail
+	return start, end
+}
+
 func countVisible(v PaneVisibility) int {
 	n := 0
 	if v.Menu {