fix(cypher): tackle #1000 IC6 residual UNWIND/MATCH gap - #1022

Summary

• keep the exact official interactive-complex-6 direct-Cypher repro anchored in one umbrella branch
• record the decomposition and current stack for #1000
• keep implementation landing work on the narrower stacked PRs instead of trying to merge this umbrella branch

Links

• Refs Cypher lowering does not support WITH ... UNWIND after MATCH-introduced graph aliases #1000
• Umbrella issue: Cypher lowering does not support WITH ... UNWIND after MATCH-introduced graph aliases #1000
• Residual repro comment: Cypher lowering does not support WITH ... UNWIND after MATCH-introduced graph aliases #1000 (comment)
• Phase 1 PR: fix(cypher): support expression-valued pattern properties #1027
• Phase 2 PR: fix(cypher): support reentry MATCH WHERE WITH #1028
• Phase 3 PR: fix(cypher): support post-WITH MATCH UNWIND #1029
• Phase 4 PR: fix(cypher): support multiple reentry WHERE stages #1032
• Phase 5 PR: fix(cypher): support scalar-only prefix MATCH reentry #1034
• Phase 6 PR: fix(cypher): support connected comma fanout #1035
• Phase 7 PR: fix(cypher): support joined-row aggregate overlap #1036
• Phase 8 PR: fix(cypher): run exact ic6 tag cooccurrence #1037

Current status

• still draft
• still the umbrella exploration / decomposition PR, not the merge vehicle
• exact benchmark-shaped RED repro remains anchored here
• the implementation stack has now advanced to a point where exact official IC6 is green on the top stacked PR

Latest outcome

• exact official interactive-complex-6 Cypher now passes in-tree on fix(cypher): run exact ic6 tag cooccurrence #1037
• dataset-backed dgx-spark host-CPU conformance rerun now reports cypher = ok
• targeted dgx-spark RAPIDS spot checks pass on the new multihop row-binding cuDF lane
• nothing in this umbrella PR is intended for merge while the stacked slices remain the real delivery path