fix: harden typed metrics review findings

crates/crank-metrics/tests/cardinality.rs

@@ -1,8 +1,9 @@
 use std::{collections::BTreeSet, time::Duration};
 
 use crank_metrics::{
-    HttpMethod, HttpRoute, HttpStatusClass, McpMethod, McpOutcome, McpResponseMode,
-    record_http_request, record_mcp_request,
+    ExemplarTraceId, HttpMethod, HttpRoute, HttpStatusClass, McpMethod, McpOutcome,
+    McpResponseMode, MetricService, record_http_request, record_mcp_request,
+    render_metric_schema_json,
 };
 use metrics_util::debugging::DebuggingRecorder;
 
@@ -13,6 +14,8 @@ fn one_million_hostile_values_collapse_to_the_same_closed_series() {
     metrics::with_local_recorder(&recorder, || {
         for index in 0..1_000_000_u32 {
             let canary = format!("workspace-{index}-request-trace-url-secret");
+            assert!(MetricService::parse(&canary).is_none());
+            assert!(ExemplarTraceId::parse(&canary).is_none());
             record_http_request(
                 HttpRoute::from_matched_path(&canary),
                 HttpMethod::classify(&canary),
@@ -36,4 +39,5 @@ fn one_million_hostile_values_collapse_to_the_same_closed_series() {
         .collect::<BTreeSet<_>>();
     assert_eq!(series.len(), 4);
     assert!(series.iter().all(|value| !value.contains("workspace-")));
+    assert!(!render_metric_schema_json().unwrap().contains("workspace-"));
 }