[Requests and ideas] Differentiate built-in slash commands with mine via UI element

### Feature summary

Small QoL improvement

### What problem are you trying to solve?

**Scenario: I want to learn about the built in slash commands**
1. I hit `/`, which opens up the list
2. Currently, the only thing differentiating commands is the type. Right now, I just have "Prompt" and ""
- By "type" I mean this part of the entry: "{command-name} {description} {type}"
3. Problem is that my global skills show up as "Prompts", as well as certain built-in ones like `/inbox`
4. This makes it ambiguous to differentiate what's mine and what's built in. It's worsened because I have a TON of skills pulled in.

For example, there's a `/research` command. Is that mine or the app's?

**Impact:** just a small papercut, but it slightly worsened the experience of trying out new slash commands.

### Proposed solution

Could be a simple UI element or styling choice. Could be some structured organization of commands.

### Workflow impact

It would just make discovery and activation of built-in slash commands better.
For example, if `/research` did a good job, do I attribute that to y'all or my own skill? Only way I find out is by searching for "research" in my machine...

### Installation context

_No response_

### Additional context

_No response_