refactor(build): reuse pageData.relativePath for the HMR payload path

Equivalent to re-applying the rewrite map manually, but hardened
against drive-letter case mismatches on Windows.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/node/plugin.ts

@@ -242,7 +242,7 @@ export async function createVitePressPlugin(
           ) {
             logDeadLinks(deadLinks, siteConfig.logger, true)
             const payload: PageDataPayload = {
-              path: `/${siteConfig.rewrites.map[relativePath] || relativePath}`,
+              path: `/${pageData.relativePath}`,
               pageData
             }
             // notify the client to update page data