fix(cypher): support post-WITH MATCH UNWIND - #1029

Summary

• implement the narrow Phase 3 #1000 slice for post-reentry WITH collect([distinct] alias) AS list UNWIND list AS alias MATCH ... RETURN
• relax bounded reentry stage accounting so a final WITH ... RETURN after the last reentry MATCH is accepted
• amplify parser/lowering coverage around the new reentry-unwind boundary cases and keep unsupported remainder explicit

Scope

This is Phase 3 of #1000, stacked on top of Phase 2 PR #1028.

What this branch now does:

• supports reentry collect -> UNWIND -> MATCH execution in the bounded reentry lane
• supports carried scalars through that reentry collect/unwind rewrite
• supports a final WITH before RETURN after the last reentry MATCH
• hardens hidden carried-column rewriting so already-hidden reentry scalar references normalize onto the current carried alias
• keeps non-collect post-reentry UNWIND ... MATCH, multi-UNWIND reentry shapes, MATCH immediately after reentry UNWIND, and final mixed-source WITH d, bid shapes as explicit boundary tests

Current status

• still draft
• implementation for the narrow Phase 3 subset is pushed
• focused parser/runtime amplification is green locally
• the exact official IC6 query now advances past the old UNWIND after post-WITH MATCH blocker and stops at the next one: Cypher only supports one WHERE clause after post-WITH MATCH in the current GFQL Cypher compiler

Links

• Refs Cypher lowering does not support WITH ... UNWIND after MATCH-introduced graph aliases #1000
• Stacked on fix(cypher): support reentry MATCH WHERE WITH #1028
• Phase 2 PR: fix(cypher): support reentry MATCH WHERE WITH #1028
• Phase 1 PR: fix(cypher): support expression-valued pattern properties #1027
• Umbrella issue: Cypher lowering does not support WITH ... UNWIND after MATCH-introduced graph aliases #1000
• Umbrella draft PR: fix(cypher): tackle #1000 IC6 residual UNWIND/MATCH gap #1022