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/main.rs

@@ -1,3 +1,5 @@
+mod access;
+mod access_service;
 mod auth;
 mod observability;
 mod tools;
@@ -38,6 +40,10 @@ async fn main() {
     // Event journal — append-only mutation log (flush every 100 events)
     let journal = journald::journal::Journal::new(store.clone(), 100);
 
+    // Access control
+    let access = access::AccessControl::new(config.auth.enabled);
+    access.register_defaults().await;
+
     // Workspace manager for agent-specific overlays
     let workspace_mgr = queryd::workspace::WorkspaceManager::new(store.clone());
     if let Err(e) = workspace_mgr.rebuild().await {
@@ -70,6 +76,7 @@ async fn main() {
         }))
         .nest("/workspaces", queryd::workspace_service::router(workspace_mgr))
         .nest("/journal", journald::service::router(journal))
+        .nest("/access", access_service::router(access))
         .nest("/tools", tools::service::router({
             let tool_reg = tools::registry::ToolRegistry::new_with_defaults();
             tool_reg.register_defaults().await;