(fix) Add stripThinkBlocks helper for reasoning tag removal

src/lib/utils/stripThinkBlocks.ts

@@ -0,0 +1,36 @@
+import { THINK_BLOCK_REGEX } from "$lib/constants/thinkBlockRegex";
+
+const THINK_OPEN_TAG = "<think>";
+const THINK_CLOSE_TAG = "</think>";
+
+export function stripThinkBlocks(text: string): string {
+	if (!text) return "";
+	THINK_BLOCK_REGEX.lastIndex = 0;
+	const result = text.replace(THINK_BLOCK_REGEX, "");
+	THINK_BLOCK_REGEX.lastIndex = 0;
+	return result;
+}
+
+export function hasUnclosedThinkBlock(text: string): boolean {
+	if (!text) return false;
+	const lastOpen = text.lastIndexOf(THINK_OPEN_TAG);
+	if (lastOpen === -1) return false;
+	const nextClose = text.indexOf(THINK_CLOSE_TAG, lastOpen);
+	return nextClose === -1;
+}
+
+export function splitThinkSegments(text: string): string[] {
+	const source = text ?? "";
+	THINK_BLOCK_REGEX.lastIndex = 0;
+	const segments = source.split(THINK_BLOCK_REGEX);
+	THINK_BLOCK_REGEX.lastIndex = 0;
+	return segments;
+}
+
+export function hasThinkSegments(text: string): boolean {
+	if (!text) return false;
+	THINK_BLOCK_REGEX.lastIndex = 0;
+	const match = THINK_BLOCK_REGEX.test(text);
+	THINK_BLOCK_REGEX.lastIndex = 0;
+	return match;
+}