bug: library writes to stdout via stray printf in load_config_clean #109

Part of #108 (health-review epic).

Problem

src/dedx.c, in load_config_clean(), contains a debug leftover:

if (config->elements_length == 0) {
    printf("error \n");
    *err = DEDX_ERR_TARGET_NOT_FOUND;
    return -1;
}

A library must never write to stdout. Any consumer that uses stdout as a data channel (CLI pipes, the WASM build, scripts) can have its output corrupted by this stray line. The printf also adds no diagnostic value — the error is already reported through *err.

Steps to reproduce

Call the API with a custom-compound configuration (target resolves to a compound not found in the embedded data) such that dedx_internal_evaluate_compound() yields elements_length == 0, then observe error printed to stdout while *err is set to DEDX_ERR_TARGET_NOT_FOUND.

Expected

No output on stdout; the error is communicated solely via *err / the return value.

Proposed change

Delete the printf("error \n"); line. (Optionally route genuine diagnostics through a caller-controlled callback in a separate issue — out of scope here.)

Acceptance criteria

• No printf/fprintf(stdout, …) calls remain in src/dedx.c.
• The not-found path still sets *err = DEDX_ERR_TARGET_NOT_FOUND and returns -1.
• grep -rn "printf" src/ | grep -v embedded/ returns nothing in non-test code.

Good first issue.