[Bug] Instance-level registration fails when a single application acts as both provider and consumer with @DubboReference(scope = "remote")

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- [x] I am sure that all the content I provide is in English.

### Search before asking

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### Apache Dubbo Component

Java SDK (apache/dubbo)

### Dubbo Version

下面是一份**可直接用于 Apache Dubbo GitHub Issue** 的英文标题与正文，表述偏工程化、可复现、符合开源社区沟通规范，也明确点出 **Instance-level registration + same app acts as provider & consumer + `@DubboReference(scope="remote")` failure** 这一关键组合条件。

---

## **Title**

Instance-level registration fails when a single application acts as both provider and consumer with `@DubboReference(scope = "remote")`

---

## **Description**

### Background

We are using **Apache Dubbo 3.x** with **instance-level (application-level) registration** enabled.

In our deployment model, **a single application instance acts as both a provider and a consumer**.
This application internally references its own exported services using:

```java
@DubboReference(scope = "remote")
```

The intention is to **force remote invocation** (even if the provider is co-located), which works correctly when **provider and consumer are deployed as separate applications**.

However, when **provider and consumer coexist in the same application instance**, the reference fails.

---

### Problem Description

Under the following conditions, the Dubbo reference fails:

* Instance-level (application-level) registration enabled
* Same application instance acts as:

* Service provider
* Service consumer
* Consumer references the service using:

```java
@DubboReference(scope = "remote")
```
* Registry: Nacos (but the issue seems independent of registry implementation)

**Observed behavior:**

* Service export succeeds
* Instance is correctly registered
* Consumer fails to resolve or invoke the remote service
* No such failure occurs when:

* Provider and consumer are deployed as **separate applications**
* Or when `scope = "local"` / default behavior is used

---

### Expected Behavior

When `scope = "remote"` is explicitly specified:

* The consumer should **always perform remote service discovery and invocation**
* Even if the provider is in the same JVM / same application instance
* Behavior should be consistent regardless of whether provider and consumer are deployed together or separately

---

### Actual Behavior

* In a **self-contained provider + consumer application**, the reference fails
* Dubbo appears to:

* Either incorrectly filter out the local instance
* Or fail to correctly resolve remote endpoints under instance-level registration
* The same configuration works correctly when provider and consumer are split into different applications

---

### Why This Is a Problem

This pattern is common in:

* Modular monoliths evolving toward microservices
* Applications using **internal RPC abstraction** for future service splitting
* Scenarios requiring **strict remote call semantics** for consistency testing, traffic routing, or governance

The current behavior makes it unsafe to use `scope = "remote"` in a self-provider-consumer scenario under instance-level registration.

---

### Questions / Suspected Cause

* Is `scope = "remote"` intentionally unsupported when provider and consumer share the same application instance?
* Is there an issue in:

* Instance filtering logic
* Self-instance exclusion
* Application-level metadata resolution
* Should `scope = "remote"` bypass local instance optimizations entirely in instance-level mode?

---

### Steps to reproduce this issue

provider yaml :
dubbo:
application:
name: nest-test
logger: slf4j
qos-enable: false
qos-accept-foreign-ip: false
protocol:
name: tri
port: 50052
registry:
address: nacos://${nacos.address:127.0.0.1}:8848
register-mode: instance

provider test code
@DubboReference(scope = "remote")
private TestDubboApi testDubboApi;

### What you expected to happen

I need to clarify whether, under instance-level registration, Dubbo intentionally does not support self-service testing using @DubboReference(scope = "remote"), or whether this behavior represents an unknown bug.

### Anything else

In this demo, the RPC invocation works correctly when the provider and the consumer are started as separate applications.

### Do you have a (mini) reproduction demo?

- [x] Yes, I have a minimal reproduction demo to help resolve this issue more effectively!

### Are you willing to submit a pull request to fix on your own?

- [x] Yes I am willing to submit a pull request on my own!

### Code of Conduct

- [x] I agree to follow this project's [Code of Conduct](https://www.apache.org/foundation/policies/conduct)

Start with the provider YAML and the `@DubboReference(scope = "remote")` reproduction described in the issue. Compare resolution and invocation when provider and consumer share one application instance versus separate applications, with instance-level registration enabled. Done means the self-provider-consumer case resolves and invokes remotely, or the limitation is documented and confirmed.

Written by the indexing model from the issue text.