blog: move markdown sibling out from under HTML page

`pageExtensions: ["ts", "tsx", "md", "mdx"]` plus a directory named `index.md/` made Next.js treat the markdown route as the index page of `[slug]/`, so `/blog/<slug>` was serving the markdown body instead of the rendered post.

Rename the directory to `raw.md/` so the segment is a literal child path (same shape as `feed.xml`) with no `index.<ext>` collision. URL becomes `/blog/<slug>/raw.md`. llms.txt updated to match.

Author: rgbkrk

app/(blog)/blog/[slug]/index.md/route.ts app/(blog)/blog/[slug]/raw.md/route.tsapp/(blog)/blog/[slug]/index.md/route.ts renamed to app/(blog)/blog/[slug]/raw.md/route.ts

@@ -15,7 +15,7 @@ export async function GET() {
     "",
     ...posts.map(
       (post) =>
-        `- [${post.title}](${absoluteUrl(`/blog/${post.slug}/index.md`)}): ${post.description}`,
+        `- [${post.title}](${absoluteUrl(`/blog/${post.slug}/raw.md`)}): ${post.description}`,
     ),
     "",
   ];