fix(pdf-download): use pdfFile.build instead of regex-transforming pdfDownloadUrl

When a compile result is served from cache (fromCache: true), pdfDownloadUrl
is set to the cached format `/download/.../build/editorId-buildId/output/cached/output.pdf`,
which doesn't match the /compressed route. pdfFile.build always contains the
raw buildId regardless of cache state, so use that to construct the URL directly.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

services/web/frontend/js/features/pdf-preview/components/pdf-hybrid-download-button.tsx

@@ -31,7 +31,7 @@ function filenameFromDisposition(disposition: string | null, ext: string) {
 }
 
 function PdfHybridDownloadButton() {
-  const { pdfDownloadUrl, pdfFile, showLogs } = useCompileContext()
+  const { pdfDownloadUrl, pdfFile, showLogs, clsiServerId } = useCompileContext()
   const { sendEvent } = useEditorAnalytics()
   const { projectId } = useProjectContext()
   const { t } = useTranslation()
@@ -67,11 +67,16 @@ function PdfHybridDownloadButton() {
     setDownloading(true)
     setDownloadError(null)
     try {
-      // Derive the compressed URL from the existing pdfDownloadUrl by appending /compressed
-      const compressedUrl = pdfDownloadUrl.replace(
-        /\/output\.pdf(\?|$)/,
-        `/output.pdf/compressed$1`
-      ) + (pdfDownloadUrl.includes('?') ? '&' : '?') + `quality=${downloadQuality}`
+      // Use pdfFile.build (always the raw buildId, even for cached compiles) so
+      // the URL matches our /compressed route regardless of fromCache state.
+      const buildId = pdfFile?.build
+      if (!buildId) {
+        setDownloadError(t('pdf_download_compression_failed'))
+        return
+      }
+      const params = new URLSearchParams({ quality: downloadQuality })
+      if (clsiServerId) params.set('clsiserverid', clsiServerId)
+      const compressedUrl = `/download/project/${projectId}/build/${buildId}/output/output.pdf/compressed?${params}`
       const response = await fetch(compressedUrl, { credentials: 'same-origin' })
       if (!response.ok) {
         setDownloadError(t('pdf_download_compression_failed'))
@@ -95,7 +100,7 @@ function PdfHybridDownloadButton() {
     } finally {
       setDownloading(false)
     }
-  }, [pdfDownloadUrl, downloadQuality, t])
+  }, [pdfDownloadUrl, pdfFile, clsiServerId, projectId, downloadQuality, t])
 
   const dismiss = useCallback(() => {
     requestIdRef.current += 1