A bounded, UTF-8 host filesystem path: a workspace/worktree root, a
worktree target, or a host-directory-browse cursor (directory/after/
parent/next_after). Mirrors the node’s own OpaqueHostPath narrowed
to its UTF-8 representation only, the same way HarnessRepositoryPathV1
narrows the node’s dual-representation RepositoryPath – see
repository_path_from_api/project_repository_path in
hatchery-harness-service for that precedent: a genuinely non-UTF-8
host path from the node is a projection failure, never silently
lossy-displayed. Validation intentionally stays as minimal as the node’s
own validate_opaque_host_path (non-empty, bounded, no NUL byte): unlike
a repository-relative path, an absolute host path legitimately contains
backslashes, drive letters, and colons (Windows), so this type imposes no
format assumptions beyond that.