Clip images to editor bounds, prevent overflow into output panel

Images that would extend past the editor content area into the
output panel or status bar are now skipped entirely. Removed the
ECH-based erase approach (doesn't clear Sixel pixels) in favor
of simply not rendering images that don't fit within the editor.

tcell's own screen redraw clears the cell-level content when
scrolling, and Sixel images only render when they fully fit.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: rlogman

internal/editor/editor.go

@@ -182,8 +182,7 @@ type Editor struct {
 
 	// Pending inline images to render after tcell draw completes.
 	// Collected during Draw(), flushed at the end via raw escape sequences.
-	pendingImages  []PendingImage
-	lastImageAreas []PendingImage // previous frame's image positions for clearing
+	pendingImages []PendingImage
 
 	// ttyFile is a handle to /dev/tty (or os.Stdout on Windows) for writing
 	// raw escape sequences that bypass tcell's screen buffer.

internal/editor/image_output.go

@@ -42,33 +42,26 @@ func (e *Editor) flushPendingImages() {
 		return
 	}
 
-	// Clear previous image areas by overwriting with spaces.
-	// This prevents Sixel pixels from persisting after scroll.
-	for _, prev := range e.lastImageAreas {
-		for r := 0; r < prev.Height; r++ {
-			row := prev.ScreenRow + r + 1 // 1-based
-			col := prev.ScreenCol + 1
-			pos := fmt.Sprintf("\033[%d;%dH", row, col)
-			_, _ = fmt.Fprint(e.ttyFile, pos)
-			// Erase from cursor to end of line within the image width
-			_, _ = fmt.Fprintf(e.ttyFile, "\033[%dX", prev.Width)
-		}
-	}
-
-	// Record current image positions for next clear cycle
-	e.lastImageAreas = make([]PendingImage, len(e.pendingImages))
-	copy(e.lastImageAreas, e.pendingImages)
+	// Get the editor's visible area to clip images
+	_, editorY, _, editorH := e.GetInnerRect()
+	// Account for tab bar + breadcrumb
+	editorContentTop := editorY + 2
+	editorContentBottom := editorY + editorH
 
 	for _, img := range e.pendingImages {
 		if img.EncodedData == "" {
 			continue
 		}
-		// Skip images that would extend below the visible area
-		_, screenH := 0, 0
-		if e.ttyFile == os.Stdout {
-			// Can't determine screen size easily; just render
+
+		// Skip images that start outside the editor content area
+		if img.ScreenRow < editorContentTop || img.ScreenRow >= editorContentBottom {
+			continue
+		}
+
+		// Skip images that would overflow past the editor bottom into output panel
+		if img.ScreenRow+img.Height > editorContentBottom {
+			continue
 		}
-		_ = screenH
 
 		// ANSI cursor positioning: ESC [ row ; col H (1-based)
 		pos := fmt.Sprintf("\033[%d;%dH", img.ScreenRow+1, img.ScreenCol+1)