Stacks: one machine, one set of files; default home is <data dir>/stacks

The hub no longer probes a node's Docker on tcp :2375, holds compose files
for a node, or runs compose against another machine's Docker. hubStacks,
nodeDocker, taskOnHub and the hub-side /api/nodes/{node}/docker/... routes
are gone; the generic node proxy hands those requests to the node's own
Ham Lab. Stack.remote / held_by and compose.Spec.Remote are removed.

New stacks default to <data dir>/stacks on every machine. Folders with two
or more deployed stacks are still offered, after it, never as default.
The ~/stacks fallback is gone. A missing home is skipped without a sudo find.

A schedule saved earlier with a tcp target is refused with a message
instead of being run against this machine's Docker.

PORTABILITY.md 3.1, 3.2, 3.3 and 9.2 done; 3.5 checked, no change needed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/api/stacks_test.go

@@ -7,6 +7,7 @@ import (
 	"testing"
 
 	"hamlab/internal/compose"
+	"hamlab/internal/config"
 	"hamlab/internal/store"
 )
 
@@ -119,3 +120,37 @@ func TestRepointSurvivesAMissingContainer(t *testing.T) {
 		t.Errorf("unresolvable spec was changed: %+v", got)
 	}
 }
+
+// Where new stacks go: Ham Lab's own <data dir>/stacks is always offered, first and as the
+// default, whether or not anything is in it yet. A folder this machine already keeps stacks
+// in — two or more deployed from it — is offered too, but never ahead of Ham Lab's own.
+func TestHomesDefaultToDataDir(t *testing.T) {
+	root := t.TempDir()
+	cfg := config.Default(filepath.Join(root, "data", "config.json"))
+	s := &Server{cfg: cfg}
+	own := filepath.Join(root, "data", "stacks")
+	legacy := filepath.Join(root, "home", "stacks", "box")
+	deployed := func(dir, name string) stack {
+		f := filepath.Join(dir, name, "compose.yaml")
+		return stack{Name: name, Containers: []string{name + "-1"}, Files: []string{f}, File: f, HostFiles: []string{f}, HostFile: f, Editable: true}
+	}
+
+	// Nothing deployed anywhere: one home, Ham Lab's own.
+	homes := s.homesOf(nil)
+	if len(homes) != 1 || homes[0].Dir != own || !homes[0].Default {
+		t.Fatalf("empty machine: homes = %+v, want just %s as default", homes, own)
+	}
+
+	// Two stacks deployed from a pre-existing folder: it is offered, after Ham Lab's own.
+	homes = s.homesOf([]stack{deployed(legacy, "a"), deployed(legacy, "b")})
+	if len(homes) != 2 || homes[0].Dir != own || !homes[0].Default || homes[1].Dir != legacy || homes[1].Default || homes[1].Stacks != 2 {
+		t.Fatalf("legacy folder: homes = %+v, want [%s (default), %s]", homes, own, legacy)
+	}
+
+	// One lone stack elsewhere says nothing about where the next should go; one in Ham Lab's
+	// own folder is already home.
+	homes = s.homesOf([]stack{deployed(filepath.Join(root, "home", "apps"), "orchestrator"), deployed(own, "c")})
+	if len(homes) != 1 || homes[0].Dir != own || homes[0].Stacks != 1 || !homes[0].Default {
+		t.Fatalf("lone stacks: homes = %+v, want just %s", homes, own)
+	}
+}