fix(audit-2026-06-11/F-SE-H-04): scrub runtime error detail from public data-plane responses

ExecError::Runtime strings (filesystem paths, "blocked by SSRF policy:
link-local" cloud-metadata reconnaissance, pool-exhaustion timing,
panic fragments, and attacker-thrown strings) were returned verbatim in
the public /api/v1/execute + user-route 502 bodies. This handler only
serves anonymous data-plane callers (the authenticated script-test path
is in manager-core and keeps verbose errors), so log the full text
server-side under a correlation id and return a stable generic message
plus the id for operator grep.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/picloud/tests/api.rs

@@ -1234,6 +1234,45 @@ async fn execution_errors_are_still_logged(pool: PgPool) {
     assert!(logs[0]["response_body"]["error"].is_string());
 }
 
+#[ignore = "needs DATABASE_URL pointing at a running Postgres"]
+#[sqlx::test(migrations = "../manager-core/migrations")]
+async fn runtime_error_detail_is_scrubbed_from_public_response(pool: PgPool) {
+    // Audit 2026-06-11 (F-SE-H-04) — a runtime error's verbose detail
+    // (here a thrown marker string, but in the wild SDK/SSRF/internal
+    // paths) must not reach the public data-plane response body. The
+    // caller gets a stable message + a correlation id; the full text
+    // only goes to the server log.
+    let (s, app_id) = server_with_app(pool).await;
+    let created: Value = s
+        .post("/api/v1/admin/scripts")
+        .json(&with_app(
+            &app_id,
+            json!({
+                "name": "leaky",
+                "source": r#"throw "SECRET_MARKER_98765""#,
+            }),
+        ))
+        .await
+        .json();
+    let id = created["id"].as_str().unwrap();
+
+    let r = s
+        .post(&format!("/api/v1/execute/{id}"))
+        .json(&json!({}))
+        .await;
+    r.assert_status(axum::http::StatusCode::BAD_GATEWAY);
+    let body: Value = r.json();
+    let err = body["error"].as_str().unwrap();
+    assert!(
+        !err.contains("SECRET_MARKER_98765"),
+        "runtime detail leaked to public response: {err}"
+    );
+    assert!(
+        err.contains("ref:"),
+        "scrubbed response should carry a correlation id, got: {err}"
+    );
+}
+
 // ============================================================================
 // v1.1.3 — Modules: scripts.kind, route + trigger rejection, end-to-end import
 // ============================================================================