Drop the unused HeaderHeight constant and dedupe the header config build

Follow-up to review feedback on the shared-header redesign:

- Remove the HeaderHeight constant. Nothing referenced it (callers compute
  height via HeaderHeightFor), and its doc described a "maximum" that
  HeaderHeightFor does not actually enforce, so the comment was misleading.
- In the view and modify View() methods, build the header config once and reuse
  it for both RenderHeader and the height reservation instead of rebuilding it
  twice per frame. The click/scroll handlers keep deriving the height from the
  same config, so the header's dimensions remain a single source of truth.

Author: skarim

internal/tui/modifyview/model.go

@@ -1361,8 +1361,13 @@ func (m Model) View() string {
 
 	// Header
 	showHeader := shared.ShouldShowHeader(m.width, m.height)
+	headerLines := 0
 	if showHeader {
-		shared.RenderHeader(&out, m.buildHeaderConfig(), m.width, m.height)
+		// Build the header config once and reuse it for both rendering and the
+		// height reservation, so View does not rebuild it twice per frame.
+		cfg := m.buildHeaderConfig()
+		shared.RenderHeader(&out, cfg, m.width, m.height)
+		headerLines = shared.HeaderHeightFor(cfg)
 	} else {
 		// The header (and its inline-image logo) is hidden; clear any logo that
 		// was previously drawn so it does not linger in the graphics layer.
@@ -1392,7 +1397,7 @@ func (m Model) View() string {
 	bottomLines := 2 // error/status line + status bar (post-scroll newline is inline)
 
 	// Scrolling — reserve space for header and fixed bottom
-	reservedLines := bottomLines + m.headerHeight()
+	reservedLines := bottomLines + headerLines
 	viewHeight := m.height - reservedLines
 	if viewHeight < 1 {
 		viewHeight = 1

internal/tui/shared/header.go

@@ -6,12 +6,6 @@ import (
 	"github.com/charmbracelet/lipgloss"
 )
 
-// HeaderHeight is the maximum number of lines the header occupies (a top border,
-// the content rows, and a bottom border). The actual height for a given config
-// is HeaderHeightFor, which sizes the box to its content with no trailing empty
-// rows.
-const HeaderHeight = 9
-
 // MinHeightForHeader is the minimum terminal height to show the header.
 const MinHeightForHeader = 25
 

internal/tui/stackview/model.go

@@ -360,8 +360,13 @@ func (m Model) View() string {
 	var out strings.Builder
 
 	showHeader := shared.ShouldShowHeader(m.width, m.height)
+	reservedLines := 0
 	if showHeader {
-		shared.RenderHeader(&out, m.buildHeaderConfig(), m.width, m.height)
+		// Build the header config once and reuse it for both rendering and the
+		// height reservation, so View does not rebuild it twice per frame.
+		cfg := m.buildHeaderConfig()
+		shared.RenderHeader(&out, cfg, m.width, m.height)
+		reservedLines = shared.HeaderHeightFor(cfg)
 	} else {
 		// The header (and its inline-image logo) is hidden; clear any logo that
 		// was previously drawn so it does not linger in the graphics layer.
@@ -392,7 +397,6 @@ func (m Model) View() string {
 	content := b.String()
 
 	// Apply scrolling
-	reservedLines := m.headerHeight()
 	viewHeight := m.height - reservedLines
 	if viewHeight < 1 {
 		viewHeight = 1