Add level_events ledger with offline Kraken run

Establishes experiments/results/level_events.jsonl (same tracked-ledger pattern as
the other result files). The single record is reproducible from the committed
Kraken BTC/USD daily dataset.

https://claude.ai/code/session_016GPBJMzif5JpfJukBMg7Te

Author: claude

experiments/results/level_events.jsonl

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+{"config_hash": "ef0f946bf9a6", "exchange": "kraken", "levels": [{"events": [], "level": "0.236", "price": 78762.7188}, {"events": [], "level": "0.382", "price": 82721.9906}, {"events": [], "level": "0.5", "price": 85921.95}, {"events": [], "level": "0.618", "price": 89121.9094}, {"events": [], "level": "0.786", "price": 93677.7838}], "n_events": 0, "run_id": "levelev_20260530T161718Z", "swing": {"bars": 462, "direction": "down", "end": {"index": 719, "kind": "low", "price": 72362.8, "prominence": 2.8557, "timestamp": "2026-05-29T00:00:00+00:00"}, "features": {"cleanliness": 0.033, "duration": 22.1, "magnitude": 0.8801, "prominence": 0.8702, "recency": 0.9986, "round_number": 0.1561, "scale_confluence": 0.5, "structure_alignment": 1.0}, "price_range": 27118.3, "score": -5.0407, "start": {"index": 257, "kind": "high", "price": 99481.1, "prominence": 2.4802, "timestamp": "2025-02-21T00:00:00+00:00"}, "status": "provisional"}, "symbol": "BTC/USD", "timeframe": "1d", "timestamp": "2026-05-30T16:17:20.870266+00:00"}