First usage of skill command from agent plugin is not recognized

Does this issue occur when all extensions are disabled?: Yes

- VS Code Version: 1.135.0
- OS Version: linux 6.18.35-gentoo-r1

Steps to Reproduce:

1. Download VSCode and extract it
2. Create inside the installation directory a new directory `data/` to create a portable version (to ensure it is a fresh copy without any settings/extensions)
3. Create new directory "someplug" for the agent plugin
```
mkdir ~/someplug/
```
4. Create a minimal `plugin.json` file with the following content inside the `~/someplug/` directory:
```
{
"name": "dummy"
}
```
5. Create the directory `skills/print-hello-world/` inside the `someplug/` directory.
```
mkdir -p ~/someplug/skills/print-hello-world
```
6. Add a `SKILL.md` file inside the directory `~/someplug/skills/print-hello-world` directory with the following content:
```
Calculate the sum of 3+3 and output it.
```
7. Go to the installation of VSCode and run `./code`.
8. Login to GitHub in the welcome screen, which appears in VSCode.
9. Close the remaining wizard of theme selection.
10. Open the settings with CTRL + ,
11. Edit the `chat.pluginLocations` setting to include the directory `~/someplug/`, set the value to `true`.
12. Enter `/print` inside the AI chat window. The auto complete popup already recognize the new plugin and its skills

13. Select the `print-hello-world` skill or press enter, the chat automatically change to `/dummy print-hello-world`. Notice how the text does not turn blue to recognize the skill, but instead displays it as normal text.

15. Press enter to send the AI chat message.

Now the AI handle the request as a normal text message, resulting in saying "Hello, World" or whatever the AI model is generating. It does NOT handle the `SKILL.md` file content.

Also notice how the coloring at the top of `/dummy print-hello-world` indicate that a skill command was executed. However, it was not.

Only the first time a skill from a custom agent plugin is not recognized immediately. After that any further usage of `/print-hello-world` (or `/dummy print-hello-world`) works perfectly.