[Feedback]: Desktop lacks support for adding custom providers (parity with CLI `Add a provider`)

首先，将 CLI 的“Add a provider”流程与 issue 中描述的 Desktop Settings 或 model-picker 流程进行比较，包括与 #25 相关的 provider 配置和 session-sync 行为。定义已知 provider、自定义 provider ID、base URL 和 API key 应如何表示。完成标准是 Desktop 能够在 Linux 上以与所请求 CLI 功能相当的方式添加并复用 provider。

What problem are you trying to solve?

In Command Code Desktop (Linux, v0.1.30) there is no equivalent to the CLI v1.54.0 flow for adding custom providers (Add a provider / provider id: ollama, work-llm, openrouter… plus the list with vercel, groq, mistral, xai, together, cerebras, ↓ 184 more).

This is what the flow looks like in the CLI:

# Command Code v1.54.0
# models: muse-spark-1.3-contributor

Add a provider
Pick a known provider below, or type your own id.

provider id: ollama, work-llm, openrouter…
  vercel · https://ai-gateway.vercel.sh/v1
  groq · https://api.groq.com/openai/v1
  mistral · https://api.mistral.ai/v1
  xai · https://api.x.ai/v1
  together · https://api.together.xyz/v1
  cerebras · https://api.cerebras.ai/v1
  ↓ 184 more

In the Desktop app there is no screen/button/command (cmd) to do the same — only the default provider/login can be used, with no way to connect third-party providers (Ollama, OpenRouter, Groq, Together, etc.).

What would improve it?

Parity with the CLI in the Desktop app:

• An "Add a provider" screen/button in Settings (or in the model picker);
• A list of known providers plus a field for a custom provider id + baseURL + API key;
• The same 190+ providers available in the CLI.

What do you do today?

I use CLI v1.54.0 in the terminal to configure the provider, but the configuration is not reflected/reusable in the Desktop app on Linux — TUI/CLI and Desktop flows seem not to sync providers/sessions (related to #25).

Context / Environment

• Desktop: v0.1.30 (latest as of 2026-09-16), Linux
• CLI: v1.54.0 (muse-spark-1.3-contributor)
• Reported on: Linux