Phase 13: Access control — role-based sensitivity enforcement

- AccessControl: agent roles with allowed sensitivity levels
- 4 default roles: admin (all), recruiter (PII ok), analyst (financial ok), agent (internal only)
- Field-level masking: determines which columns to mask per agent based on sensitivity
- Query audit log: tracks every query with agent, datasets, PII fields accessed
- Endpoints: GET/POST /access/roles, GET /access/audit, POST /access/check
- Toggleable via config (auth.enabled)
- 100K embedding: supervisor now sustained 125/sec (2.9x vs single pipeline)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/gateway/src/access_service.rs

@@ -0,0 +1,62 @@
+use axum::{
+    Json, Router,
+    extract::{Query, State},
+    http::StatusCode,
+    response::IntoResponse,
+    routing::{get, post},
+};
+use serde::Deserialize;
+
+use crate::access::{AccessControl, AgentRole};
+
+pub fn router(ac: AccessControl) -> Router {
+    Router::new()
+        .route("/roles", get(list_roles))
+        .route("/roles", post(set_role))
+        .route("/audit", get(query_audit))
+        .route("/check", post(check_access))
+        .with_state(ac)
+}
+
+async fn list_roles(State(ac): State<AccessControl>) -> impl IntoResponse {
+    Json(ac.list_roles().await)
+}
+
+async fn set_role(
+    State(ac): State<AccessControl>,
+    Json(role): Json<AgentRole>,
+) -> impl IntoResponse {
+    let name = role.agent_name.clone();
+    ac.set_role(role).await;
+    (StatusCode::OK, format!("role set: {name}"))
+}
+
+#[derive(Deserialize)]
+struct AuditQuery {
+    limit: Option<usize>,
+}
+
+async fn query_audit(
+    State(ac): State<AccessControl>,
+    Query(q): Query<AuditQuery>,
+) -> impl IntoResponse {
+    Json(ac.recent_audit(q.limit.unwrap_or(50)).await)
+}
+
+#[derive(Deserialize)]
+struct CheckRequest {
+    agent: String,
+    sensitivity: shared::types::Sensitivity,
+}
+
+async fn check_access(
+    State(ac): State<AccessControl>,
+    Json(req): Json<CheckRequest>,
+) -> impl IntoResponse {
+    let allowed = ac.can_access(&req.agent, &req.sensitivity).await;
+    Json(serde_json::json!({
+        "agent": req.agent,
+        "sensitivity": req.sensitivity,
+        "allowed": allowed,
+    }))
+}