fix: handle __404__ sentinel in github-dockerfile-discovery (#25)

- search_org_dockerfiles: add __404__ to the existing __422__ guard so
  orgs with no code-search access are skipped cleanly instead of trying
  to jq-parse the sentinel string
- fetch_dockerfile_content: check for __404__ and __422__ alongside the
  empty-string guard to avoid a misleading 'Unexpected encoding' warning
  when a file is not found

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: locus313

enterprise/github-dockerfile-discovery/github-dockerfile-discovery.sh

@@ -136,7 +136,7 @@ search_dockerfiles_in_org() {
     local resp
     resp=$(gh_api "/search/code?q=filename:Dockerfile+org:${org}&per_page=100&page=${page}")
 
-    if [ "${resp}" = "__422__" ]; then
+    if [[ "${resp}" == "__422__" || "${resp}" == "__404__" ]]; then
       print_warning "  Code search not available for org '${org}'. Skipping."
       return 0
     fi
@@ -282,7 +282,7 @@ fetch_and_parse_dockerfile() {
 
   resp=$(gh_api "/repos/${repo_full_name}/contents/${encoded_path}" 2>/dev/null || echo "")
 
-  if [ -z "${resp}" ]; then
+  if [[ -z "${resp}" || "${resp}" == "__404__" || "${resp}" == "__422__" ]]; then
     print_warning "    Could not fetch ${repo_full_name}/${path}"
     return 0
   fi