GFQL/Cypher: expose validate-only API (compile/bind checks without execution) #1320

Summary

Expose an API to validate Cypher/GFQL queries without executing them, so clients can run parser+binder+static-schema checks as a preflight step.

Why

Current validation exists in compile/binder lanes (e.g., #1302) but is not surfaced as a first-class user API for "check-only" workflows (IDE/lint/CI/pre-submit).

Scope

In scope:

• Add a public validate-only entrypoint (name TBD, e.g. g.validate_cypher(...))
• Run parse/lower/bind/schema-validation pipeline without dispatching runtime execution
• Return structured diagnostics (errors/warnings, stage, span/alias/property context)
• Support strict/permissive behavior aligned with native-types rollout controls

Out of scope:

• Query execution or result materialization
• New language features beyond existing parser/compiler support

Acceptance

1. Validate-only API returns success/failure + structured diagnostics and never executes query operators.
2. Strict-mode failures match binder/schema checks from GFQL native types T2: binder-time schema validation in strict mode #1302 lane behavior.
3. Tests prove no side effects / no runtime execution in validate-only mode.
4. Docs include examples for local/CI usage.

Related

• Umbrella: [FEA] GFQL native type system: schemas, inference, validation, and Arrow representation #1046
• Program meta: Meta: #1046 native type-system staged decomposition program #1262
• Rollout lane: GFQL native types T5: adoption gates, strict/permissive rollout, and CI/docs receipts #1311
• Current validation foundations: GFQL native types T2: binder-time schema validation in strict mode #1302, GFQL native types T3: propagate nullability/type metadata through bound/logical plan seams #1300, GFQL native types T3.b: migrate inline nullable patterns onto ir.metadata helpers #1309, GFQL native types T4: Arrow/type bridge contracts and coercion semantics #1312
• Execution DAG: Meta: GFQL compiler/planner post-M4 execution DAG (active wave) #1259