Allow overriding theme-internal components from .vitepress/theme without Vite alias

[lorlike]

Is your feature request related to a problem? Please describe.

I want to be able to fully customize the theme from the .vitepress/theme directory only, without changing any files outside that directory (including build/config files such as vite.config.js).

Describe the solution you'd like

Allow adding a configuration file inside the theme that can remap or override internal theme component imports (i.e. provide alias-like behavior from within the theme).

Describe alternatives you've considered

No response

Additional context

No response

Validations

• Follow our Code of Conduct
• Read the docs.
• Read the Contributing Guidelines.
• Check that there isn't already an issue that asks for the same feature to avoid creating a duplicate.