chore: add FFI boundary audit + gnn_training integration test

- audits/assail-classifications.a2ml: panic-attack classification registry for legitimate FFI patterns (24 unsafe blocks in ffi/mod.rs, spark_axiom.rs, proof_search.rs)
- audits/audit-ffi-boundary.md: detailed FFI boundary safety audit with per-module SAFETY justification
- tests/gnn_training_integration_test.rs: integration test loading Julia-generated metrics and applying to health status

All files previously untracked from earlier audit + integration test work.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

Author: hyperpolymath

audits/assail-classifications.a2ml

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+; SPDX-License-Identifier: PMPL-1.0-or-later
+; Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
+;
+; Classification registry for panic-attack assail findings that are confirmed
+; legitimate patterns and should not be treated as actionable weak-points.
+;
+; Format mirrors the panic-attack user-classification registry protocol.
+; Cross-reference: audits/audit-ffi-boundary.md
+
+(assail-classifications
+
+  ; ─── src/rust/ffi/mod.rs — C-ABI exports + raw-pointer handling ──────────
+  (classification
+    (file "src/rust/ffi/mod.rs")
+    (category "UnsafeCode")
+    (audit "audits/audit-ffi-boundary.md §1")
+    (rationale "C-ABI exports for the Zig FFI layer; 24 documented unsafe blocks reviewed in linked audit"))
+
+  (classification
+    (file "src/rust/ffi/mod.rs")
+    (category "ResourceLeak")
+    (audit "audits/audit-ffi-boundary.md §1")
+    (rationale "Box::into_raw ownership-transfer to Zig caller; Zig calls rust_free_* to drop — not an actual leak"))
+
+  ; ─── src/rust/ffi/spark_axiom.rs — Rust→SPARK via C ABI ─────────────────
+  (classification
+    (file "src/rust/ffi/spark_axiom.rs")
+    (category "UnsafeCode")
+    (audit "audits/audit-ffi-boundary.md §2")
+    (rationale "extern C callouts to SPARK-compiled policy enforcement; pointer preconditions enforced by Ada contracts"))
+
+  ; ─── src/rust/proof_search.rs — Chapel FFI, feature-gated ───────────────
+  (classification
+    (file "src/rust/proof_search.rs")
+    (category "UnsafeCode")
+    (audit "audits/audit-ffi-boundary.md §3")
+    (rationale "Chapel parallel-search FFI behind #[cfg(feature = chapel)]; all 7 unsafe blocks reviewed in linked audit"))
+
+  ; ─── src/interfaces/graphql/ffi_wrapper.rs ────────────────────────────────
+  (classification
+    (file "src/interfaces/graphql/ffi_wrapper.rs")
+    (category "UnsafeCode")
+    (audit "audits/audit-ffi-boundary.md §4")
+    (rationale "Interface-layer wrapper over src/rust/ffi/mod.rs C-ABI; CStr/raw-pointer patterns identical to §1"))
+
+  ; ─── src/interfaces/grpc/ffi_wrapper.rs ───────────────────────────────────
+  (classification
+    (file "src/interfaces/grpc/ffi_wrapper.rs")
+    (category "UnsafeCode")
+    (audit "audits/audit-ffi-boundary.md §4")
+    (rationale "Interface-layer wrapper over src/rust/ffi/mod.rs C-ABI; CStr/raw-pointer patterns identical to §1"))
+
+  ; ─── src/interfaces/rest/ffi_wrapper.rs ───────────────────────────────────
+  (classification
+    (file "src/interfaces/rest/ffi_wrapper.rs")
+    (category "UnsafeCode")
+    (audit "audits/audit-ffi-boundary.md §4")
+    (rationale "Interface-layer wrapper over src/rust/ffi/mod.rs C-ABI; CStr/raw-pointer patterns identical to §1"))
+
+)

audits/audit-ffi-boundary.md

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+<!--
+SPDX-License-Identifier: PMPL-1.0-or-later
+Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
+-->
+
+# FFI Boundary Audit
+
+**Auditor**: Jonathan D.A. Jewell  
+**Date**: 2026-04-26  
+**Scope**: all `unsafe` blocks in the echidna Zig/SPARK/Chapel FFI boundary
+
+---
+
+## §1 — `src/rust/ffi/mod.rs` (UnsafeCode, ResourceLeak)
+
+The ffi/mod.rs module exports 24 documented `unsafe` blocks for the Zig FFI
+layer.  Each unsafe block has an inline `// SAFETY:` comment.  The patterns:
+
+- **C-ABI exports** (`pub unsafe extern "C" fn …`) — required by Zig and
+  any C consumer to call Rust across the ABI boundary.
+- **Raw pointer → Rust reference** (`CStr::from_ptr`, `slice::from_raw_parts`)
+  — caller contract: non-null, correctly-aligned, valid-lifetime pointer
+  supplied by the Zig shim (enforced by the Zig wrapper in `src/zig_ffi/`).
+- **ResourceLeak**: The one finding is a raw pointer returned from
+  `Box::into_raw`; the callee (Zig side) owns the allocation and calls
+  `rust_free_*` to drop it.  This is the standard Rust→C ownership-transfer
+  pattern, not an actual leak.
+
+**Classification**: legitimate FFI.  No remediation required.
+
+---
+
+## §2 — `src/rust/ffi/spark_axiom.rs` (UnsafeCode)
+
+Two `extern "C"` callouts to SPARK-compiled policy enforcement routines
+(`echidna_spark_enforce_policy`, `echidna_spark_worst_danger`,
+`echidna_spark_max_usages`).  The module docstring confirms:
+
+- Never passes null — `slice.as_ptr()` on a non-empty slice is always non-null.
+- Length is bounded by `wire.len()` which comes from a bounded Vec.
+- SPARK-side preconditions checked with Ada contracts.
+
+**Classification**: legitimate FFI (Rust→SPARK via C ABI).  No remediation required.
+
+---
+
+## §3 — `src/rust/proof_search.rs` (UnsafeCode, feature-gated Chapel)
+
+Seven unsafe blocks, ALL behind `#[cfg(feature = "chapel")]`.  Patterns:
+
+- `CString::new(goal).context(…)` — only unsafe via the `extern "C"` call site.
+- `CStr::from_ptr` on Chapel-returned strings — caller contract: Chapel runtime
+  guarantees null-terminated string lifetime until next Chapel call.
+- `extern "C"` callouts to the Chapel parallel search runtime.
+
+If `chapel` feature is not enabled, no unsafe code compiles in.
+
+**Classification**: legitimate FFI (Rust→Chapel via Zig shim, feature-gated).  No remediation required.
+
+---
+
+## §4 — `src/interfaces/*/ffi_wrapper.rs` (UnsafeCode × 6)
+
+The three interface crates (graphql, grpc, rest) each contain an `ffi_wrapper.rs`
+that calls into the core Rust FFI layer via `CStr`/`CString` and raw pointer
+manipulation.  All six findings are structurally identical to §1 — they are
+wrappers that adapt the C-ABI output of `src/rust/ffi/mod.rs` to Rust-safe
+types for the interface handlers.
+
+**Classification**: legitimate FFI (interface-layer wrappers over §1 boundary).  No remediation required.

tests/gnn_training_integration_test.rs

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+// SPDX-License-Identifier: PMPL-1.0-or-later
+// GNN training pipeline integration test
+
+#[cfg(test)]
+mod gnn_training_integration_tests {
+    use echidna::diagnostics::{HealthStatus, load_training_metrics, update_health_with_metrics};
+    use std::path::Path;
+
+    /// Test: Load metrics from actual training file and update health
+    #[test]
+    fn test_load_and_apply_training_metrics() {
+        // Load metrics from the file generated by Julia training
+        let metrics_path = Path::new("models/training_metrics.json");
+        
+        if !metrics_path.exists() {
+            println!("⚠ Training metrics file not found at {:?}", metrics_path);
+            println!("Run: julia src/julia/train_and_evaluate.jl");
+            return;
+        }
+        
+        let metrics = load_training_metrics(metrics_path)
+            .expect("Failed to load training metrics");
+        
+        // Verify metrics were parsed correctly
+        assert_eq!(metrics.status, "completed");
+        assert!(metrics.nDCG > 0.0, "nDCG should be > 0");
+        assert!(metrics.MRR > 0.0, "MRR should be > 0");
+        assert_eq!(metrics.epochs_trained, 50);
+        assert!(metrics.training_data_size > 0);
+        
+        // Create health status and apply metrics
+        let mut health = HealthStatus::new();
+        
+        // Before update, GNN is not loaded
+        assert!(!health.gnn_model_health.is_loaded);
+        assert_eq!(health.gnn_model_health.last_validation_nDCG, 0.0);
+        
+        // Apply metrics
+        update_health_with_metrics(&mut health, &metrics);
+        
+        // After update, GNN should be loaded with real metrics
+        assert!(health.gnn_model_health.is_loaded);
+        assert_eq!(health.gnn_model_health.last_validation_nDCG, metrics.nDCG);
+        assert_eq!(health.gnn_model_health.last_validation_MRR, metrics.MRR);
+        assert!(health.gnn_model_health.nDCG_meets_threshold);
+        assert!(health.gnn_model_health.last_trained.is_some());
+        
+        // Verify health percentage is now higher (GNN contributes 20%)
+        let health_pct = health.health_percentage();
+        assert!(health_pct >= 20.0, "With GNN loaded at {:.2}, health should be >= 20%", metrics.nDCG);
+        
+        println!("✓ Training metrics loaded successfully");
+        println!("  nDCG:  {}", metrics.nDCG);
+        println!("  MRR:   {}", metrics.MRR);
+        println!("  Health: {:.1}%", health_pct);
+    }
+}