fix: capture bound function result in instrumentDO

The bind() method returns a new bound function but the code was
discarding the return value. This caused 'Illegal invocation' errors
when calling Durable Object methods via RPC.

Fixes method binding for Cloudflare Workers RPC calls and PartyServer
.name property access.

Author: grrowl

src/instrumentation/do.ts

@@ -1,17 +1,17 @@
-import { context as api_context, trace, SpanOptions, SpanKind, Exception, SpanStatusCode } from '@opentelemetry/api'
+import { context as api_context, Exception, SpanKind, SpanOptions, SpanStatusCode, trace } from '@opentelemetry/api'
 import { SemanticAttributes } from '@opentelemetry/semantic-conventions'
+import { Initialiser, setConfig } from '../config.js'
+import { DOConstructorTrigger } from '../types.js'
 import { passthroughGet, unwrap, wrap } from '../wrap.js'
+import { instrumentStorage } from './do-storage.js'
+import { instrumentEnv } from './env.js'
 import {
-	getParentContextFromHeaders,
 	gatherIncomingCfAttributes,
 	gatherRequestAttributes,
 	gatherResponseAttributes,
+	getParentContextFromHeaders,
 	instrumentClientFetch,
 } from './fetch.js'
-import { instrumentEnv } from './env.js'
-import { Initialiser, setConfig } from '../config.js'
-import { instrumentStorage } from './do-storage.js'
-import { DOConstructorTrigger } from '../types.js'
 
 import { DurableObject as DurableObjectClass } from 'cloudflare:workers'
 
@@ -217,8 +217,8 @@ function instrumentDurableObject(
 			} else {
 				const result = Reflect.get(target, prop)
 				if (typeof result === 'function') {
-					result.bind(doObj)
-					return instrumentAnyFn(result, initialiser, env, state.id)
+					const boundResult = result.bind(doObj)
+					return instrumentAnyFn(boundResult, initialiser, env, state.id)
 				}
 				return result
 			}