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CallStats gains stall_ms/stall_count (None = no stall observation); winner sample triple (wall, stall_ms, stall_count) converted once in _attempt success branch; net = max(0, wall - stall) converged into the shared _record_winner_sample used by both the single-path guard and hedge winner registration. Two-fail hedge rounds record nothing (no winner to attribute). Design section 4.2; issues #27.