store: drop in-flight when drain+fence exceeds until

[rearden-grok]

Summary

• Mainnet IBD at 26% (height 258870) blacklisted a valid block: leftover miss_on=body with identity at fk past drain_fk while Class C/fence had already run ahead.
• PR store: stamp in-flight until at TipOnly start; drop on Class C #273 pruned in-flight CreatePin layers when Class C tip ≥ until. This restores the drop gate to drain+fence height > until (HeightFence::drain_and_fence_hi = min of drain height and fence tip).
• until is still stamped at note_layer (lookup_started_hi). Equality keeps. Class C tip is not a drop gate.

Test plan

• drain_and_fence_hi_is_min_of_drain_height_and_fence_tip (fence tip 40, drain on height 2 → 2)
• prune_keeps_until_drain_fence_exceeds_stamped_until / confirm twin (keep at == until; drop at +1; drain lag keeps)
• inflight_binds_after_drain_before_fence / inflight_binds_after_fence_before_drain
• confirm_engine_pins_spend_of_just_written_pack
• required CI green (fmt deny clippy ast-grep test windows macos multinode coverage)

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