feat: Renamed textBuffer to assistantTextBuffer in headless.ts and vali…

- src/headless.ts
- .sf/REQUIREMENTS.md

SF-Task: S01/T04

src/headless.ts

@@ -754,7 +754,7 @@ async function runHeadlessOnce(
 		| { costUsd: number; inputTokens: number; outputTokens: number }
 		| undefined;
 	let thinkingBuffer = "";
-	let textBuffer = "";
+	let assistantTextBuffer = "";
 	// Drop only adjacent identical formatProgress output. A widget that
 	// re-emits the same setStatus on every LLM call would otherwise print
 	// the same line N times in a row. Two different lines still both show;
@@ -1270,7 +1270,7 @@ async function runHeadlessOnce(
 				}
 				// Non-verbose: accumulate text_delta for truncated one-liner
 				else if (ame?.type === "text_delta") {
-					textBuffer += String(ame.delta ?? ame.text ?? "");
+					assistantTextBuffer += String(ame.delta ?? ame.text ?? "");
 				}
 			}
 
@@ -1299,9 +1299,9 @@ async function runHeadlessOnce(
 				!options.verbose &&
 				(eventType === "tool_execution_start" || eventType === "message_end")
 			) {
-				if (textBuffer.trim()) {
-					writeHeadlessLine(formatTextLine(textBuffer));
-					textBuffer = "";
+				if (assistantTextBuffer.trim()) {
+					writeHeadlessLine(formatTextLine(assistantTextBuffer));
+					assistantTextBuffer = "";
 				}
 				if (thinkingBuffer.trim()) {
 					writeHeadlessLine(formatThinkingLine(thinkingBuffer));