fix(paperclip-runner): resolve mockup path relative to capture script location

Co-Authored-By: Paperclip <noreply@paperclip.ing>

packages/paperclip-runner/docs/design/mockups/capture-issue-thread-mockup.mjs

@@ -1,7 +1,7 @@
 import { chromium } from "@playwright/test";
 import { mkdirSync } from "node:fs";
 
-const root = new URL("./packages/paperclip-runner/docs/design/mockups/phase-7-issue-thread.html", import.meta.url).href;
+const root = new URL("./phase-7-issue-thread.html", import.meta.url).href;
 const outDir = process.env.OUT_DIR;
 mkdirSync(outDir, { recursive: true });