refactor(text): share code-region parsing for reasoning tags

src/shared/text/code-regions.ts

@@ -0,0 +1,31 @@
+export interface CodeRegion {
+  start: number;
+  end: number;
+}
+
+export function findCodeRegions(text: string): CodeRegion[] {
+  const regions: CodeRegion[] = [];
+
+  const fencedRe = /(^|\n)(```|~~~)[^\n]*\n[\s\S]*?(?:\n\2(?:\n|$)|$)/g;
+  for (const match of text.matchAll(fencedRe)) {
+    const start = (match.index ?? 0) + match[1].length;
+    regions.push({ start, end: start + match[0].length - match[1].length });
+  }
+
+  const inlineRe = /`+[^`]+`+/g;
+  for (const match of text.matchAll(inlineRe)) {
+    const start = match.index ?? 0;
+    const end = start + match[0].length;
+    const insideFenced = regions.some((r) => start >= r.start && end <= r.end);
+    if (!insideFenced) {
+      regions.push({ start, end });
+    }
+  }
+
+  regions.sort((a, b) => a.start - b.start);
+  return regions;
+}
+
+export function isInsideCode(pos: number, regions: CodeRegion[]): boolean {
+  return regions.some((r) => pos >= r.start && pos < r.end);
+}