docs(dod): enforce markdownlint rule for markdown files

.githooks/pre-commit

@@ -5,6 +5,7 @@ failed=0
 cr=$(printf '\r')
 
 staged_shell_files=$(git diff --cached --name-only --diff-filter=ACMR | grep -E '\.sh$' || true)
+staged_markdown_files=$(git diff --cached --name-only --diff-filter=ACMR | grep -E '\.md$' || true)
 
 for file in $staged_shell_files; do
   mode=$(git ls-files --stage -- "$file" | awk '{print $1}')
@@ -19,6 +20,20 @@ for file in $staged_shell_files; do
   fi
 done
 
+if [ -n "$staged_markdown_files" ]; then
+  if ! command -v markdownlint >/dev/null 2>&1; then
+    echo "ERROR: markdownlint is required to validate staged Markdown files (.md)." >&2
+    echo "Install with npm: npm install --global markdownlint-cli" >&2
+    failed=1
+  else
+    # Validate the staged markdown files currently present in the working tree.
+    # This keeps the hook simple and fast for standard project usage.
+    if ! markdownlint $staged_markdown_files; then
+      failed=1
+    fi
+  fi
+fi
+
 if [ "$failed" -ne 0 ]; then
   echo "Pre-commit check failed." >&2
   exit 1