Space: what is using a disk, WizTree-style

Pick a disk, not a partition; the scan walks every filesystem it backs, as root when
the host allows, in a helper process that streams the tree back. A tree of folders
largest-first over a treemap of the selected folder, nested to the file and coloured by
kind, plus the thousand largest files. The rail no longer offers the hub-only pages
while a remote machine is being looked at.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

cmd/hamlab/main.go

@@ -33,6 +33,7 @@ import (
 	"hamlab/internal/nodes"
 	"hamlab/internal/services"
 	"hamlab/internal/setup"
+	"hamlab/internal/space"
 	"hamlab/internal/storage"
 	"hamlab/internal/store"
 	"hamlab/internal/tasks"
@@ -75,6 +76,8 @@ func main() {
 	switch cmd { // commands that don't read the config
 	case "fs": // privileged helper for the Files tab (run as root by the daemon)
 		os.Exit(files.Helper(flag.Args()[1:], os.Stdin, os.Stdout, os.Stderr))
+	case "space-walk": // helper for the Space tab: measure mountpoints, stream the tree back
+		os.Exit(space.Helper(flag.Args()[1:], os.Stdout, os.Stderr))
 	case "install", "uninstall":
 		var err error
 		if cmd == "install" {