Support colocated jujutsu / git repositories

[devurandom]

Describe the bug

Since Jujutsu 0.34.0, jj will created colocated jj/git repositories (meaning both .jj/ and .git/ exist) by default: https://docs.jj-vcs.dev/latest/changelog/#0340-2025-10-01

treefmt however detects the repository type as git as soon as .git/ is present, ignoring the presence of .jj/:

treefmt/walk/walk.go

Lines 213 to 222 in 0a2f334

	switch walkType {
	case Auto:
	// for now, we keep it simple and try git first, jujutsu second, and filesystem last
	reader, err = NewReader(Git, root, path, db, statz)
	if err != nil {
	reader, err = NewReader(Jujutsu, root, path, db, statz)
	if err != nil {
	reader, err = NewReader(Filesystem, root, path, db, statz)
	}
	}

To Reproduce

Steps to reproduce the behavior:

1. jj git clone ...
2. Move around files
3. Run treefmt and see it complain about "Path ... is in the worktree but appears to have been removed from the filesystem"

Expected behavior

treefmt detects colocated jj/git repositories as jj repositories.

System information

NixOS 25.11, jj 0.35.0, treefmt 2.4.0