fix(llms): use ':' separator in llms.txt link entries

llmstxt.org specifies a link entry as `[name](url)` optionally
followed by `:` and notes. The generated `## Documentation` and
`## Examples` tables used an em dash instead.

Conforming to the spec also makes the generated scaffolding pure
ASCII. This does not make llms.txt ASCII-only overall -- prose from
`description` and consumer markdown passes through untouched -- so
sites must still serve the file as `text/plain; charset=utf-8` to
avoid mojibake.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: jaysin586

src/lib/vite/llms.ts

@@ -293,10 +293,11 @@ async function buildIndex(opts: ResolvedOptions): Promise<string> {
         ''
     )
     for (const e of entries) {
-        // Format: `- [Title](mirror.md) — canonical HTML URL`
+        // Format: `- [Title](mirror.md): canonical HTML URL`
+        // The `:` separator is what llmstxt.org specifies for link notes.
         // Both URLs are useful — the .md is the citation surface, the
         // HTML URL is what the LLM should deep-link humans to.
-        lines.push(`- [${e.title}](${opts.siteUrl}${e.route}.md) — ${opts.siteUrl}${e.route}`)
+        lines.push(`- [${e.title}](${opts.siteUrl}${e.route}.md): ${opts.siteUrl}${e.route}`)
     }
     if (exampleEntries.length > 0) {
         lines.push(
@@ -308,7 +309,7 @@ async function buildIndex(opts: ResolvedOptions): Promise<string> {
             ''
         )
         for (const e of exampleEntries) {
-            lines.push(`- [${e.title}](${opts.siteUrl}${e.route}.md) — ${opts.siteUrl}${e.route}`)
+            lines.push(`- [${e.title}](${opts.siteUrl}${e.route}.md): ${opts.siteUrl}${e.route}`)
         }
     }
     if (appendBody) {