fix: strip docs/ prefix from links when building site

The README links to docs/roadmap.md which works on GitHub/Tangled,
but when copied to site-out/docs/ context, the path became double-prefixed.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[e-mail]>

scripts/build-wisp-docs.mjs

···
   if (!(await exists(docsIndex))) {
     const readme = path.join(repoRoot, "README.md");
     if (await exists(readme)) {
-      const md = await readFile(readme, "utf8");
+      let md = await readFile(readme, "utf8");
+      // Strip docs/ prefix from links since we're now inside the docs context.
+      md = md.replace(/\]\(docs\//g, "](");
       await writeFile(path.join(outDocsDir, "index.md"), md, "utf8");
       pages.push({
         path: "index.md",