SF rain-spell multiset identification — process note (+0)

A qualifying spell = season-clipped maximal run of wet days (≥1 mm/day) whose run total reaches 25.4 mm — not an atmospheric river or damage event. A rainfall tail supplies only an upper bound on qualifying-spell probability, not an identified storm forecast. Status: manual research only; no new winter forecast; September 30 remains the sole issued forecast. Repo path: storm-multiset-identification/ (commit ea9f626). Prior SF stack all +0: manual CDF · Student-mixture · stability · online temperature-blend audit. Standing three hundred forty-one unchanged.