fix(cypher): close #1000 exact ic6 residual stack - #1039

Closes #1000

This is the final landing PR for the validated stacked #1000 decomposition.

What it brings to master:

• expression-valued pattern properties
• reentry MATCH ... WHERE ... WITH support
• post-WITH MATCH UNWIND support
• multiple reentry WHERE stages
• scalar-only prefix WITH ... MATCH reentry
• connected comma-pattern fanout around post
• joined-row aggregate overlap handling
• exact interactive-complex-6 / tag-cooccurrence Cypher support

Validation already completed on the stacked slices before this landing PR:

• full PR CI green on the constituent stack
• focused local retest on this exact landing branch tree: 26 passed, 3 skipped
• DGX host CPU benchmark: exact IC6 cypher = ok
• targeted DGX RAPIDS spot check attempted; blocked by immediate environmental CUDA OOM on the host, not by a correctness regression

Stack references:

• fix(cypher): support expression-valued pattern properties #1027
• fix(cypher): support reentry MATCH WHERE WITH #1028
• fix(cypher): support post-WITH MATCH UNWIND #1029
• fix(cypher): support multiple reentry WHERE stages #1032
• fix(cypher): support scalar-only prefix MATCH reentry #1034
• fix(cypher): support connected comma fanout #1035
• fix(cypher): support joined-row aggregate overlap #1036
• fix(cypher): run exact ic6 tag cooccurrence #1037
• umbrella draft: fix(cypher): tackle #1000 IC6 residual UNWIND/MATCH gap #1022