feat(input): use RAG/운곡교P1입력.xlsx as the P1 input

- public/samples/운곡교P1입력.xlsx is a byte copy of RAG/운곡교P1입력.xlsx
- loadP1 and the sample loader read the three-sheet input
- spec workbook (intent.PR) stays for the single-sheet regression tests
- test: input file has sheets 교각 · IP · 받침 and parses to P1 with no issues

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>

src/main.ts

@@ -492,7 +492,7 @@ function openImport(): void {
 }
 
 async function fetchSample(): Promise<Uint8Array> {
-  const res = await fetch(new URL('samples/P1.xlsx', document.baseURI));
+  const res = await fetch(new URL('samples/운곡교P1입력.xlsx', document.baseURI));
   if (!res.ok) throw new Error(`샘플 응답 ${res.status}`);
   return new Uint8Array(await res.arrayBuffer());
 }
@@ -535,7 +535,7 @@ $<HTMLInputElement>('file').addEventListener('change', async (ev) => {
 });
 $<HTMLButtonElement>('pick-sample').addEventListener('click', async () => {
   try {
-    loadBytes(await fetchSample(), '샘플 P1 (Pier ui_xxx.xlsx)');
+    loadBytes(await fetchSample(), '샘플 P1 (운곡교P1입력.xlsx)');
   } catch (err) {
     setStatus(`샘플을 불러오지 못했습니다: ${(err as Error).message}`);
   }