fix: ensure lesson_count/LESSON_COUNT is always a single integer

Use `$(grep ...) || var=0` assignment pattern so that:
- zero matches (grep exits 1, prints "0"): || branch sets var=0 correctly
- missing file (grep exits 2, prints nothing): || branch sets var=0
- matches found (grep exits 0, prints N): var=N, || branch skipped
This avoids the "0\n0" double-value produced by the old `|| echo 0`
pattern when grep prints "0" and then the fallback also prints "0".

Agent-Logs-Url: https://github.com/TUBAF-IfI-LiaScript/TUBAF-IfI-LiaScript.github.io/sessions/5c24d93a-7262-46db-93d4-c7e22d69854c

Co-authored-by: vgoehler <1705385+vgoehler@users.noreply.github.com>

Author: Copilot

Makefile

@@ -51,7 +51,7 @@ download-pdfs-%:
 	@if [ -n "$(filter $*,$(PDF_COURSES))" ]; then \
 		mkdir -p .cache; \
 		[ -x scripts/download_upstream_pdfs.sh ] || chmod +x scripts/download_upstream_pdfs.sh; \
-		LESSON_COUNT=$$(grep -c '^[[:space:]]*- url:' "$*.yml" 2>/dev/null || true); \
+		LESSON_COUNT=$$(grep -c '^[[:space:]]*- url:' "$*.yml" 2>/dev/null) || LESSON_COUNT=0; \
 		if bash scripts/download_upstream_pdfs.sh "$*"; then \
 			if [ -f ".cache/$*_upstream_pdfs" ]; then \
 				UPSTREAM_COUNT=$$(wc -l < ".cache/$*_upstream_pdfs" | tr -d ' '); \

scripts/generate_courses.sh

@@ -29,7 +29,7 @@ for course in "${course_list[@]}"; do
     # Try to download upstream PDFs (creates/updates the manifest)
     if bash "$SCRIPT_DIR/download_upstream_pdfs.sh" "$course"; then
       # Count lessons and compare with upstream PDF coverage
-      lesson_count=$(grep -c '^[[:space:]]*- url:' "$yaml_file" 2>/dev/null || true)
+      lesson_count=$(grep -c '^[[:space:]]*- url:' "$yaml_file" 2>/dev/null) || lesson_count=0
       if [ -f "$manifest" ]; then
         upstream_count=$(wc -l < "$manifest" | tr -d ' ')
       else