datalets v0.6.0 — long fits are never blind

Big-data fits used to go dark for hours outside a terminal. No more:

• Per-task lines in plain mode (logs, CI, servers, captured notebooks): [37/104] cluster 4 · xgboost · stage 12m08s, throttled to stay log-friendly.
• Heartbeat: after 30 quiet seconds — ⏳ still working · stage elapsed 1h02m · 96/104 tasks done · waiting on global · random_forest — naming the exact task blocking the stream.
• Live bar now shows stage-elapsed time on every frame; clusterer="auto" narrates each config it tries.
• Selectable auto-search algorithms: clusterer=["kmeans", "gmm", "birch"] runs the utility-scored search over exactly those — the way to skip slow density-based clusterers on large data.

491 tests. CHANGELOG.md