Fix terminal output last line clipping in chat terminal tool progress (#308842)

fix #307571

Author: meganrogge

src/vs/workbench/contrib/chat/browser/widget/chatContentParts/media/chatTerminalToolProgressPart.css

@@ -177,7 +177,7 @@ div.chat-terminal-content-part.progress-step > div.chat-terminal-output-containe
 	background: inherit;
 }
 .chat-terminal-output-body {
-	padding: 5px 0px 1px;
+	padding: 5px 0px 3px;
 	max-width: 100%;
 	box-sizing: border-box;
 	min-height: 0;

src/vs/workbench/contrib/chat/browser/widget/chatContentParts/toolInvocationParts/chatTerminalToolProgressPart.ts

@@ -1479,13 +1479,17 @@ class ChatTerminalToolOutputSection extends Disposable {
 		const scrollableDomNode = this._scrollableContainer.getDomNode();
 		const rowHeight = this._computeRowHeightPx();
 		const padding = this._getOutputPadding();
-		const minHeight = rowHeight * MIN_OUTPUT_ROWS + padding;
 		const maxHeight = rowHeight * MAX_OUTPUT_ROWS + padding;
 		const contentHeight = this._getOutputContentHeight(lineCount, rowHeight, padding);
 		const clampedHeight = Math.min(contentHeight, maxHeight);
-		const measuredBodyHeight = Math.max(this._outputBody.clientHeight, minHeight);
-		const appliedHeight = Math.min(clampedHeight, measuredBodyHeight);
-		scrollableDomNode.style.height = appliedHeight < maxHeight ? `${appliedHeight}px` : '';
+		// Use the line-count-based calculation directly rather than constraining by
+		// _outputBody.clientHeight. The DOM measurement races with xterm's async
+		// rendering — when new lines arrive, clientHeight reflects the stale
+		// (pre-render) size, causing the viewport to be too short and clipping the
+		// last line. The calculated height still has enough headroom because it
+		// includes the output padding and may round slightly differently from
+		// xterm's actual rendered cell height.
+		scrollableDomNode.style.height = clampedHeight < maxHeight ? `${clampedHeight}px` : '';
 		this._scrollableContainer.scanDomNode();
 	}
 
@@ -1512,9 +1516,7 @@ class ChatTerminalToolOutputSection extends Disposable {
 
 	private _getOutputContentHeight(lineCount: number, rowHeight: number, padding: number): number {
 		const contentRows = Math.max(lineCount, MIN_OUTPUT_ROWS);
-		// Always add an extra row for buffer space to prevent the last line from being cut off during streaming
-		const adjustedRows = contentRows + 1;
-		return (adjustedRows * rowHeight) + padding;
+		return (contentRows * rowHeight) + padding;
 	}
 
 	private _getOutputPadding(): number {