feat(filepicker): add support for abstracted filesystem io/fs.FS [v2]

[dolmen]

Add an optional io/fs.FS to filepicker's model to allow to browse an abstracted filesystem as an alternative to the full filesystem exposed by the os package.

The filepicker API is extended (and generalized thanks to io/fs.FS), without any breaking change.

This allows for example to browse limited a subdirectory by using os.Root (go1.24+):

fp := filepicker.New()
root, _ := os.OpenRoot(dir)
fp.FS = root.FS()

Fixes #815.
Replaces #759 (which was for v1).
Discussion: #886.

Full support of symlinks is implemented. To resolve symlinks we use io/fs.ReadLink introduced with Go 1.25, but fallback to an internal implementation if the FS doesn't implement it.

By the way, references to os types and constants which are aliases to same symbols in io/fs are replaced: os.Mode*, os.DirEntry.

Example

See package github.com/dolmen-go/iofs-shell.

Runnable example:

$ go run github.com/dolmen-go/iofs-shell/examples/browse-zip@main <file>.zip

To use my fork right now:

$ go mod edit -replace=charm.land/bubbles/v2=github.com/dolmen-go/bubbles.fork/v2@v2.1.1-0.20260413112845-8dad07786efc

• I have read CONTRIBUTING.md.
• I have created a discussion that was approved by a maintainer (for new features).