[DEL] D3 remove stale reentry failfast scaffolding

[lmeyerov]

Summary

Deletion slice D3: remove stale Cypher reentry failfast scaffolding and no-longer-reachable branches.

Scope

• Identify legacy failfast branches introduced as temporary guards in reentry/refactor waves and delete those now unreachable under landed semantics.
• Retain only failfasts for truly unsupported shapes with active issue refs.

Acceptance

• Net LOC decrease (target ~500+ LOC).
• Reentry test suites and tck-gfql remain green.

Related

• Parent deletion meta (2K+ LOC wave)
• Meta: GFQL compiler/planner post-M4 execution DAG (active wave) #1259

[lmeyerov]

PR #1433 is ready for review: #1433

Status:

• implemented conservative D3 cleanup slice
• review-skill pass converged with 0 blocker / 0 important / 0 suggestion findings
• GitHub Actions and ReadTheDocs are green, including tck-gfql
• PR marked ready for review

Scope note:

• This removes the stale reentry.runtime compatibility shim, moves tests off old private reentry compatibility import paths, and lifts the closed-Cypher/GFQL: forward bounded-reentry carry hidden columns across reentry-source rebinding (LDBC SNB IC3) #1256 aggregate reentry failfast with positive row assertions.
• It is intentionally conservative around [DEL] D2 remove pre-strict binder compatibility guards after #1357 #1420 binder/pre-strict guard overlap.
• Net deletion is smaller than the aspirational ~500 LOC target, so after merge [DEL] D3 remove stale reentry failfast scaffolding #1421 should either close as the accepted D3 slice or remain open for a follow-up deletion pass.

Local validation caveat:

• cudf/GPU tests were not run locally because this host has no CUDA device; GPU/cuDF confidence should come from CI/DGX as needed.

[lmeyerov]

Closed via merged PR #1433: #1433

Merge receipt:

• merged at 2026-05-14T23:38:47Z
• merge commit 8556b82dadbc73ad0b4d54fdcdb6e2536af8ab0d
• CI green, including tck-gfql, GFQL lanes, cypher strict/parity/surface gates, broad Python matrix, and ReadTheDocs
• review-skill loop converged with 0 blocker / 0 important / 0 suggestion findings

Delivered D3 cleanup:

• removed obsolete graphistry.compute.gfql.cypher.reentry.runtime compatibility re-export shim
• moved tests off stale private reentry compatibility import paths
• lifted stale closed-Cypher/GFQL: forward bounded-reentry carry hidden columns across reentry-source rebinding (LDBC SNB IC3) #1256 chained-reentry aggregate failfast
• converted the two aggregate regression locks to positive row assertions
• preserved active unsupported-shape failfasts and avoided [DEL] D2 remove pre-strict binder compatibility guards after #1357 #1420 binder/pre-strict overlap

Meta trackers updated: #1419, #1259, #992.

[lmeyerov]

Closed after merged PR #1433: #1433