S5: add CI growth guards for lowering/CompiledCypher surfaces (#1306)

[lmeyerov]

Summary

• add a dedicated CI guardrail for Cypher monolith shrinkdown S5 metrics
• track and gate growth for:
  • lowering.py total LOC
  • CompiledCypherQuery / CompiledGraphBinding / CompiledCypherGraphQuery dataclass field and @Property counts
• document intentional baseline refresh workflow for approved growth

Changes

• added script: bin/ci_cypher_surface_guard.py
• added baseline: bin/ci_cypher_surface_guard_baseline.json
• added CI job: cypher-frontend-surface-guard in .github/workflows/ci.yml
• chained guard into cypher-frontend-ci-gates
• added docs section in DEVELOP.md with baseline refresh command

Guard policy

• fails if current lowering.py line count exceeds baseline max
• fails if any tracked CompiledCypher* field/property count exceeds baseline max
• allows intentional growth by updating baseline in the same PR with rationale

Validation

• python bin/ci_cypher_surface_guard.py
• ./bin/ruff.sh bin/ci_cypher_surface_guard.py
• ./bin/pytest.sh graphistry/tests/compute/gfql/cypher/test_lowering_s3_split_guard.py -q

Refs #1306
Parent #1260