feat(opencode): implement isInConfig semantics for additive provider management

OpenCode uses additive provider management where providers can exist in
the database but not necessarily in the live opencode.json config. This
commit implements proper isInConfig state:

Backend:
- Add get_opencode_live_provider_ids command to query live config

Frontend:
- Add getOpenCodeLiveProviderIds API method
- ProviderList queries live provider IDs and computes isInConfig
- ProviderCard receives and passes isInConfig to ProviderActions
- ProviderActions already handles the add/remove button logic

src-tauri/src/commands/provider.rs

@@ -339,3 +339,13 @@ pub fn import_opencode_providers_from_live(state: State<'_, AppState>) -> Result
     crate::services::provider::import_opencode_providers_from_live(state.inner())
         .map_err(|e| e.to_string())
 }
+
+/// 获取 OpenCode live 配置中的供应商 ID 列表
+///
+/// 用于前端判断供应商是否已添加到 opencode.json
+#[tauri::command]
+pub fn get_opencode_live_provider_ids() -> Result<Vec<String>, String> {
+    crate::opencode_config::get_providers()
+        .map(|providers| providers.keys().cloned().collect())
+        .map_err(|e| e.to_string())
+}

src-tauri/src/lib.rs

@@ -877,6 +877,7 @@ pub fn run() {
             commands::sync_universal_provider,
             // OpenCode specific
             commands::import_opencode_providers_from_live,
+            commands::get_opencode_live_provider_ids,
             // Global upstream proxy
             commands::get_global_proxy_url,
             commands::set_global_proxy_url,