Remove CEF: the web content crate, ElyMark's page, their packaging, licences and tests (C14.5)

PRD and agents.md name the native route; ElyMail's body will not use
CEF or Electron. ElyMark's package carries the KaTeX fonts' OFL.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

scripts/ci.sh

@@ -40,11 +40,9 @@ if [ -n "${ELY_SHARE:-}" ]; then
 else
   scripts/fetch-references.sh
   ${inside[@]+"${inside[@]}"} scripts/build-mupdf.sh
-  ${inside[@]+"${inside[@]}"} scripts/fetch-cef.sh
   ${inside[@]+"${inside[@]}"} scripts/build-git.sh
   ${inside[@]+"${inside[@]}"} scripts/fetch-git-lfs.sh
   ${inside[@]+"${inside[@]}"} scripts/fetch-tessdata.sh
-  ${inside[@]+"${inside[@]}"} scripts/build-mark-content.sh
   ${inside[@]+"${inside[@]}"} scripts/build-libreoffice.sh
 fi