Move the wrapper cursors to the cursor module - #823
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The `enter` wrapper had two halves. One presents a wrapped trace and batch, rewriting descriptions and compaction frontiers through `Refines`; it names no keys and no values. The other navigates the wrapped batch with a cursor. This moves the second half to `trace/cursor/wrappers/enter.rs`, leaving `trace/wrappers/enter.rs` free of any cursor mention. A reader who declines cursors keeps the wrapper and supplies its own module beside this one. The cursor reaches the wrapped batch through a new `inner()` accessor. It sits in its own unbounded impl block because the `Cursor` impl does not know that the wrapped storage is a `BatchReader`. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
As with `enter`, the wrapper splits into a half that presents a wrapped trace and batch and a half that navigates it. The second half moves to `trace/cursor/wrappers/frontier.rs`. The time semantics stay with the batch, as `advance_time`, which advances a time by `since` and reports whether `until` suppresses it. Any reader of the wrapped batch applies that rule, whether or not it reads through a cursor. The cursor no longer keeps its own copies of the two frontiers, so it holds nothing but the cursor it forwards to. Its bound strengthens to `Storage: BatchReader<Time = C::Time>`, which is what lets it hand its owned time to the batch. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
`advance_time` borrowed `since` from the batch on every time it advanced. The borrow is a slice construction and the comparisons are unchanged, but it put a call boundary inside the per-update closure, where the prior code hoisted both frontiers above it. The batch now lends its frontiers as an `Advance`, which a reader acquires once and applies to each time. The semantics still belong to the batch, so a reader that does not use cursors still gets them. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
This reverts commit 2960609. The borrowed frontiers are `Antichain<Time>`, never a time container, so borrowing one per time costs a slice construction from an inlined method rather than anything a container layout could make expensive. The `Advance` type was not worth its own name. `advance_time` keeps an `#[inline]`, matching the forwarders around it. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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Migrate the cursor-specific aspects of traces wrappers (enter and frontier) from their definitions to a
cursor/wrappersmodule, as part of relocating as much cursor-specific content to be literally cursor adjacent, rather than throughout the codebase.