fix: Deduplicate installed local and remote curated plugins (#25681)

## Summary
- Deduplicate installed `openai-curated` and `openai-curated-remote`
plugin conflicts by feature flag.
- Prefer remote when remote plugins are enabled; otherwise prefer local,
while preserving one-sided installs.

## Testing
- `just fmt`
- `git diff --check`
- Targeted `just test` was blocked locally because `cargo-nextest` is
not installed.

codex-rs/app-server/tests/suite/v2/plugin_list.rs

@@ -180,6 +180,107 @@ enabled = true
     Ok(())
 }
 
+#[tokio::test]
+async fn plugin_installed_prefers_remote_curated_conflicts_when_remote_plugin_enabled() -> Result<()>
+{
+    let codex_home = TempDir::new()?;
+    let server = MockServer::start().await;
+    write_openai_curated_marketplace(codex_home.path(), &["linear", "calendar"])?;
+    write_installed_plugin(&codex_home, "openai-curated", "linear")?;
+    write_installed_plugin(&codex_home, "openai-curated", "calendar")?;
+    std::fs::write(
+        codex_home.path().join("config.toml"),
+        format!(
+            r#"chatgpt_base_url = "{}/backend-api/"
+
+[features]
+plugins = true
+remote_plugin = true
+plugin_sharing = false
+
+[plugins."linear@openai-curated"]
+enabled = true
+
+[plugins."calendar@openai-curated"]
+enabled = true
+"#,
+            server.uri()
+        ),
+    )?;
+    write_chatgpt_auth(
+        codex_home.path(),
+        ChatGptAuthFixture::new("chatgpt-token")
+            .account_id("account-123")
+            .chatgpt_user_id("user-123")
+            .chatgpt_account_id("account-123"),
+        AuthCredentialsStoreMode::File,
+    )?;
+    let mut global_installed_body: serde_json::Value = serde_json::from_str(
+        &remote_installed_plugin_body("", "1.2.3", /*enabled*/ true),
+    )?;
+    let mut remote_only = global_installed_body["plugins"][0].clone();
+    remote_only["id"] = serde_json::json!("plugins~Plugin_11111111111111111111111111111111");
+    remote_only["name"] = serde_json::json!("remote-only");
+    remote_only["release"]["display_name"] = serde_json::json!("Remote Only");
+    global_installed_body["plugins"]
+        .as_array_mut()
+        .expect("installed plugins should be an array")
+        .push(remote_only);
+    let global_installed_body = serde_json::to_string(&global_installed_body)?;
+    mount_remote_installed_plugins(&server, "GLOBAL", &global_installed_body).await;
+    mount_remote_installed_plugins(&server, "WORKSPACE", empty_remote_installed_plugins_body())
+        .await;
+
+    let mut mcp = McpProcess::new(codex_home.path()).await?;
+    timeout(DEFAULT_TIMEOUT, mcp.initialize()).await??;
+
+    let request_id = mcp
+        .send_plugin_installed_request(PluginInstalledParams {
+            cwds: None,
+            install_suggestion_plugin_names: None,
+        })
+        .await?;
+
+    let response: JSONRPCResponse = timeout(
+        DEFAULT_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(request_id)),
+    )
+    .await??;
+    let response: PluginInstalledResponse = to_response(response)?;
+
+    let local_marketplace = response
+        .marketplaces
+        .iter()
+        .find(|marketplace| marketplace.name == "openai-curated")
+        .expect("expected openai-curated marketplace entry");
+    assert_eq!(
+        local_marketplace
+            .plugins
+            .iter()
+            .map(|plugin| plugin.id.clone())
+            .collect::<Vec<_>>(),
+        vec!["calendar@openai-curated".to_string()]
+    );
+    let remote_marketplace = response
+        .marketplaces
+        .iter()
+        .find(|marketplace| marketplace.name == "openai-curated-remote")
+        .expect("expected openai-curated-remote marketplace entry");
+    assert_eq!(
+        remote_marketplace
+            .plugins
+            .iter()
+            .map(|plugin| plugin.id.clone())
+            .collect::<Vec<_>>(),
+        vec![
+            "linear@openai-curated-remote".to_string(),
+            "remote-only@openai-curated-remote".to_string(),
+        ]
+    );
+    assert_eq!(response.marketplace_load_errors, Vec::new());
+    Ok(())
+}
+
 #[tokio::test]
 async fn plugin_installed_ignores_local_cache_without_catalog() -> Result<()> {
     let codex_home = TempDir::new()?;