feat(core-shared): OtelTracer impl using @opentelemetry/api

Implements OtelTracer as ITracer replacement for SentryTracer. Uses
@opentelemetry/api's trace.getTracer + startActiveSpan, maps span.op to
a span attribute, catches exceptions via recordException + setStatus(ERROR),
and filters null attribute values. Five Vitest tests covering name/attributes,
nesting, exception recording, status mapping, and null filtering.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pnpm-lock.yaml

@@ -542,6 +542,9 @@ importers:
         specifier: ^3.24.0
         version: 3.25.76
     devDependencies:
+      '@opentelemetry/context-async-hooks':
+        specifier: ^1.28.0
+        version: 1.28.0(@opentelemetry/api@1.9.1)
       '@repo/core-eslint':
         specifier: workspace:*
         version: link:../core-eslint