fix: pin asciidoctor to 3.0.4 to fix PDF build

Asciidoctor.js 4.0.0 (released ~June 23, 2026) breaks the
@antora/pdf-extension@1.0.0-beta.14 PDF generation, causing
ENOENT for discover.pdf during container verification.

Pin to the last known working version (3.0.4) until the
pdf-extension is updated for asciidoctor 4.x compatibility.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: gtrivedi88

Containerfile

@@ -88,7 +88,7 @@ RUN set -x \
     && npm install --no-save --global asciidoctor-kroki \
     && npm install --no-save --global gulp gulp-cli gulp-connect \
     && npm install --no-save --global js-yaml \
-    && npm install --no-save --global asciidoctor \
+    && npm install --no-save --global asciidoctor@3.0.4 \
     && which antora \
     && antora --version \
     && rm /tmp/* --recursive --force