feat(deno): Export metrics API from Deno SDK (#19305)

## Summary

- Add `metrics` to the `@sentry/core` re-export block in
`packages/deno/src/index.ts`
- The `metrics` namespace is already exported from `@sentry/core` and
re-exported by `@sentry/node`, but was missing from the Deno SDK

## Test plan

- [x] `yarn build:dev:filter @sentry/deno` passes
- [x] `cd packages/deno && yarn test` — all 12 tests pass
- [x] `eslint src/index.ts` — no lint issues

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Closes #19307 (added automatically)

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: sergical

.gitignore

@@ -54,6 +54,7 @@ tmp.js
 packages/deno/build-types
 packages/deno/build-test
 packages/deno/lib.deno.d.ts
+deno.lock
 
 # gatsby
 packages/gatsby/gatsby-node.d.ts

codecov.yml

@@ -14,3 +14,6 @@ coverage:
     patch:
       default:
         enabled: no
+
+ignore:
+  - 'packages/deno/**'

packages/deno/src/index.ts

@@ -1,6 +1,7 @@
 export type {
   Breadcrumb,
   BreadcrumbHint,
+  Metric,
   PolymorphicRequest,
   RequestEventData,
   SdkInfo,
@@ -89,6 +90,7 @@ export {
   updateSpanName,
   wrapMcpServerWithSentry,
   featureFlagsIntegration,
+  metrics,
 } from '@sentry/core';
 
 export { DenoClient } from './client';

packages/deno/test/mod.test.ts

@@ -1,8 +1,8 @@
-import type { Event } from '@sentry/core';
-import { createStackParser, nodeStackLineParser } from '@sentry/core';
+import type { Envelope, Event } from '@sentry/core';
+import { createStackParser, forEachEnvelopeItem, nodeStackLineParser } from '@sentry/core';
 import { assertEquals } from 'https://deno.land/std@0.202.0/assert/assert_equals.ts';
 import { assertSnapshot } from 'https://deno.land/std@0.202.0/testing/snapshot.ts';
-import { DenoClient, getCurrentScope, getDefaultIntegrations } from '../build/esm/index.js';
+import { DenoClient, getCurrentScope, getDefaultIntegrations, metrics, Scope } from '../build/esm/index.js';
 import { getNormalizedEvent } from './normalize.ts';
 import { makeTestTransport } from './transport.ts';
 
@@ -74,6 +74,43 @@ Deno.test('captureMessage twice', async t => {
   await assertSnapshot(t, ev);
 });
 
+Deno.test('metrics.count captures a counter metric', async () => {
+  const envelopes: Array<Envelope> = [];
+  const client = new DenoClient({
+    dsn: 'https://233a45e5efe34c47a3536797ce15dafa@nothing.here/5650507',
+    integrations: getDefaultIntegrations({}),
+    stackParser: createStackParser(nodeStackLineParser()),
+    transport: makeTestTransport(envelope => {
+      envelopes.push(envelope);
+    }),
+  });
+
+  client.init();
+  const scope = new Scope();
+  scope.setClient(client);
+
+  metrics.count('test.counter', 5, { scope });
+
+  await client.flush(2000);
+
+  // deno-lint-ignore no-explicit-any
+  let metricItem: any = undefined;
+  for (const envelope of envelopes) {
+    forEachEnvelopeItem(envelope, item => {
+      const [headers, body] = item;
+      if (headers.type === 'trace_metric') {
+        metricItem = body;
+      }
+    });
+  }
+
+  assertEquals(metricItem !== undefined, true);
+  assertEquals(metricItem.items.length, 1);
+  assertEquals(metricItem.items[0].name, 'test.counter');
+  assertEquals(metricItem.items[0].type, 'counter');
+  assertEquals(metricItem.items[0].value, 5);
+});
+
 Deno.test('App runs without errors', async _ => {
   const cmd = new Deno.Command('deno', {
     args: ['run', '--allow-net=some-domain.com', './test/example.ts'],