Epic: persistent rules are incrementally maintained views; everything else is a query (E0) #305

Problem. Persistent rules are stored definitions that every read recompiles and re-derives from base facts in a fresh timely dataflow (src/storage_engine/snapshot.rs:302-405, src/lib.rs:1481-1775, src/code_generator/mod.rs:390,707,1079). Subscriptions re-run their query per relevant commit and diff full results (src/protocol/subscription/reevaluate.rs:124-153). The "incremental engine" mirrors base relations only, is never enabled on the server path, and no rule is compiled into it (src/storage_engine/mod.rs:2318-2350, src/storage_engine/catalog_change.rs:424-429). Measured on the benchmark host at 1M edges: one-row bound read of a view 62 ms (non-recursive) / 2.9 s (recursive); write->delta with one subscriber 70 ms / 3.0 s; ten keyed subscribers on a recursive view 30 s CPU per write and 11.5 GB RSS. A differential-dataflow maintainer of the same rules applies a change in ~100 µs at every size. The docs claim the maintained behaviour.

Target. One per-knowledge-graph view maintainer (long-lived differential dataflow fed from the commit path at the commit's revision) holds every persistent rule as an arrangement; queries import arrangements at a stated revision and never re-derive; subscriptions are keyed diffs of a view between revisions; the cost probe disappears; docs tell the truth. Report Sections 1, 2 and 5.

Acceptance. Every benchmark in report Section 9 (B1-B23, including the vector bars B17-B23) passes in the perf gate on the benchmark host; the differential oracle shows 0 divergences across recursion, negation, aggregates and deletes; rule_evaluations is 0 for reads of deployed views; the docs-truth issue is closed; engine.views default is maintained and the recompute path for persistent rules is deleted.

Children (train order). Slot 1: D1, V0, V1. Slot 2: V2, V3, V4. Slot 3: V5, V6, V7. Slot 4: V9, V13, V10. Slot 5: V11, V12, V14. Slot 6: V15, V16, V18. Slot 7: VV1, VV2, VV3. Slot 8: VV4, VV5, VV6. Slot 9: VV7, V19, V20.

Supersedes. #143 (and its children #180-#187 map one-to-one onto V2, V3, V4, V5, V5, V7, V10, V9+V20); the DD remainder of #133; #238 (bar kept as B15); #276, #289 and #252 (probe-machinery defects removed by V11). Keeps #292 open until B15 passes. Depends on #296 (runaway-query fix) merging before V9. Size: epic. Order: 0.