Guard string literal token assembly

This prevents overflow during lexing and extends robust string-escape
cases.

Author: jserv

src/lexer.c

@@ -508,6 +508,8 @@ token_t lex_token_internal(bool aliasing)
                     token_str[i - 1] = next_char;
                 }
             } else {
+                if (i >= MAX_TOKEN_LEN - 1)
+                    error("String literal too long");
                 token_str[i++] = next_char;
             }
             if (next_char == '\\')

tests/driver.sh

@@ -3659,6 +3659,21 @@ int main() {
 }
 EOF
 
+# String literal and escape coverage (additional)
+try_output 0 "AZ" << 'EOF'
+int main() {
+    printf("%s", "\\x41Z"); /* hex escape then normal char */
+    return 0;
+}
+EOF
+
+try_output 0 "AZ" << 'EOF'
+int main() {
+    printf("%s", "A\\132"); /* octal escape for 'Z' */
+    return 0;
+}
+EOF
+
 # Cast zero value
 try_ 0 << EOF
 int main() {