@slidev/cli fails to recognize themes packages in two scenarios when installed with pnpm

[gepz]

Describe the bug

Slidev fails to recognize the default theme in two scenarios when using pnpm:

1. When installed globally (pnpm add -g @slidev/cli @slidev/theme-default)
2. When installed locally but running on files outside the project folder (pnpm exec slidev /path/to/outside/test.md)
   The same setups work correctly when using npm.

Minimal reproduction

Scenario 1 (Global):

1. Install slidev globally using pnpm:

pnpm add -g @slidev/cli @slidev/theme-default

2. Run slidev /path/to/file.md

Scenario 2 (Local):

1. Create a project with local slidev installation:

mkdir slidev-test
cd slidev-test
pnpm init
pnpm add @slidev/cli @slidev/theme-default

2. Run pnpm exec slidev /path/to/outside/test.md on a file outside the project directory

Both scenarios result in: "The theme "@slidev/theme-default" was not found in your project, do you want to install it now?"
Environment

• Slidev version: ^0.50.0-beta.10
• Browser: N/A (CLI issue)
• OS: Linux