Enhancement: Run Server in nix develop

[Sooryasanand]

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

When working in a Nix-based development environment (nix develop), Frontmatter CMS’s built-in server functionality does not appear to inherit the shell environment. As a result, attempting to launch the development server via the extension UI fails or behaves inconsistently. This breaks the expected development workflow for projects using Nix for reproducibility and dependency management.

Describe the solution you'd like

I’d like Frontmatter CMS to recognize and integrate with the nix develop shell context when running the dev server. This could be implemented in one of the following ways:

• Provide an option to specify a custom command or shell context for server start
• Detect whether the workspace is inside a Nix shell and spawn processes accordingly
• Allow configuration to disable internal server start and delegate to external terminal-based commands, with status integration if possible

This would make the CMS more compatible with reproducible development environments and declarative tooling setups.

Describe alternatives you've considered

• Manually running npm run start (or equivalent) in a terminal that’s already inside a nix develop shell. This works but disconnects the CMS UI from the server process.
• Overriding shell environments in the extension or editor, which introduces brittleness and doesn't generalize well across systems or team workflows.

Additional context

Nix-based setups are increasingly common in projects that prioritize reproducibility and environment isolation. Seamless support for nix develop workflows would reduce friction for developers working in these ecosystems and align Frontmatter CMS more closely with declarative infrastructure paradigms.

[estruyf]

Nix is indeed not part of the predefined list, but you are able to configure the start command with the following setting: frontMatter.framework.startCommand. Once set, you should be able to start the local server from the FM Actions panel.