fix(bitscrambler): reject malformed program headers

Validate BitScrambler program headers against the supported format and
hardware limits before using header-derived instruction and LUT sizes.
Also add regression coverage for malformed headers and document that the
program blob must come from a trusted assembler output.

components/esp_driver_bitscrambler/include/driver/bitscrambler.h

@@ -73,6 +73,11 @@ void bitscrambler_free(bitscrambler_handle_t handle);
 /**
  * @brief Load a BitScrambler binary program into BitScrambler memory
  *
+ * @note The program blob is expected to come from a trusted BitScrambler assembler
+ *       output. This API validates the header fields against hardware limits, but it
+ *       does not take an explicit blob length and therefore cannot verify that an
+ *       arbitrary caller-supplied buffer is complete.
+ *
  * @param handle BitScrambler handle
  * @param program Binary program to load
  *