add continuation to multilinebuffer

internal/viewport/linebuffer/multilinebuffer.go

@@ -112,6 +112,22 @@ func (m MultiLineBuffer) Take(
 		currentBufferIdx++
 	}
 
+	// apply continuation indicators if needed
+	if len(continuation) > 0 {
+		contentToLeft := startWidth > 0
+		contentToRight := m.totalWidth-startWidth > takeWidth-remainingWidth
+
+		if contentToLeft || contentToRight {
+			continuationRunes := []rune(continuation)
+			if contentToLeft {
+				result = replaceStartWithContinuation(result, continuationRunes)
+			}
+			if contentToRight {
+				result = replaceEndWithContinuation(result, continuationRunes)
+			}
+		}
+	}
+
 	return result, takeWidth - remainingWidth
 }
 

internal/viewport/linebuffer/multlinebuffer_test.go

@@ -106,7 +106,37 @@ func TestMultiLineBuffer_Take(t *testing.T) {
 			highlightStyle: lipgloss.NewStyle(),
 			expected:       "",
 		},
-		// TODO LEO: continuation, highlight style, other keys
+		{
+			name:           "hello world with continuation at end",
+			key:            "hello world",
+			startWidth:     0,
+			takeWidth:      7,
+			continuation:   "...",
+			toHighlight:    "",
+			highlightStyle: lipgloss.NewStyle(),
+			expected:       "hell...",
+		},
+		{
+			name:           "hello world with continuation at start",
+			key:            "hello world",
+			startWidth:     4,
+			takeWidth:      7,
+			continuation:   "...",
+			toHighlight:    "",
+			highlightStyle: lipgloss.NewStyle(),
+			expected:       "...orld",
+		},
+		{
+			name:           "hello world with continuation both ends",
+			key:            "hello world",
+			startWidth:     2,
+			takeWidth:      7,
+			continuation:   "...",
+			toHighlight:    "",
+			highlightStyle: lipgloss.NewStyle(),
+			expected:       "... ...",
+		},
+		// TODO LEO: highlight style, other keys
 	}
 
 	for _, tt := range tests {