Graphics debug log: also log what is drawn, optionally to a file

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019reK4DUGYqDUjniWYJvwUW

internal/ui/cover.go

@@ -259,6 +259,7 @@ type coverView struct {
 	*tview.Box
 	style      coverStyle
 	gfx        *kittyGraphics // real images; nil for block characters only
+	lastDrawn  [5]int         // id, position and size of the last real image drawn, for the debug log
 	cellAspect func() float64 // height of a terminal cell divided by its width
 	img        *image.RGBA
 	note       string // shown instead of the image: "loading…", "no cover"
@@ -405,6 +406,12 @@ func (c *coverView) drawGraphics(screen tcell.Screen, x, y, cols, rows int) bool
 	if err != nil {
 		return false
 	}
+	if c.gfx.debug != nil {
+		if drawn := [5]int{int(id), x, y, cols, rows}; drawn != c.lastDrawn {
+			c.lastDrawn = drawn
+			c.gfx.debug(fmt.Sprintf("draw: id %d at column %d, row %d over %dx%d cells", id, x, y, cols, rows))
+		}
+	}
 	for row := 0; row < rows; row++ {
 		for col := 0; col < cols; col++ {
 			ch, comb, style := placeholderCell(id, row, col)