verbose trace: log at DEBUG so callers can hide it from INFO sinks

The 1-row demo block (prompt + think + nudge + prefill + scored token +
64-token free continuation) used logger.info, which meant any caller
wrapping the function in an INFO-level sink (e.g. an agent harness)
got the full trace in their stdout. Downgrade to logger.debug so it
still lands in the user's verbose log but doesn't leak to agents.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/tinymfv/guided.py

@@ -212,14 +212,15 @@ def _rollout_kv_fork(
     for j, (nudge, prefill) in enumerate(scoring_slots):
         suf_ids = suf_ids_for(nudge, prefill)
         if verbose:
+            # DEBUG, not INFO: keeps the trace in the user's verbose sidecar
+            # but out of any downstream INFO sink the caller might be wrapping.
             full_text = sp_per_row[0] + tok.decode(suf_ids[0], skip_special_tokens=False)
-            # Free-form generate to see what the model actually says after the prefill.
             full_ids = torch.tensor(
                 [sp_ids_per_row[0] + suf_ids[0]], device=device, dtype=torch.long,
             )
             gen = model.generate(full_ids, max_new_tokens=64, do_sample=False, pad_token_id=pad_id)
             free = tok.decode(gen[0, full_ids.shape[1]:], skip_special_tokens=False)
-            logger.info(
+            logger.debug(
                 f"--- slot {j} (nudge={nudge!r}, prefill={prefill!r}) ---\n"
                 f"{full_text}<<<MODEL CONTINUES>>>{free}\n--- end slot {j} ---"
             )