Per-system bundles, and Android's start problem closed by narrowing it

Two gaps.

The bundle's contents are per system even though its mechanism is not, so there
are now three: substrate-arch.lock, substrate-alpine.lock and
substrate-android.lock. All three are embedded and a host reads only the one it
was built for. Arch and Alpine remain placeholders -- the closure for a one-node
mesh is still research 011/012's open question, and inventing it here would be
worse than an honest placeholder.

Android's is not a placeholder. It says a partial host cannot raise a mesh and
why: every step of a bootstrap is a package, a container, or an action against
one, and those are exactly the shapes it refuses. So a partial host can JOIN a
mesh and cannot BE the first node. That belongs where somebody looking for the
android bundle will find it.

Also separated two things that were being conflated: "this system has no
bundle" and "this system was never built". Loading a bundle for debian is not
ErrEmpty, and the test asserts they differ.

0062 -- a host may be episodic. There is no way to keep a process running on an
ordinary Android device: init needs root, a foreground service can be killed
for memory. The answer is not to fight that. It is that being killed IS
disconnection, which ADR 0036 already made an ordinary situation -- and
everything the design does for a laptop that closes is what an episodic host
needs, at a shorter period. An authoritative local store, reconcile on start,
last-heard-from reported without an alarm.

So the gap closes by requiring less rather than building something. No keep-
alive, no Android daemon, no fighting the platform's process management.

Two consequences recorded rather than glossed. Last-heard-from is a much weaker
signal on an episodic host, so a healthy phone reads as a dead server unless
the reader knows which kind it is looking at. And a declaration may take a long
time to land, which makes 0058's separation of outstanding from failed
load-bearing rather than tidy.

Left open deliberately: how an episodic host is actually started, and -- first --
what an Android node is for. Building the start mechanism before deciding that
would be building it for nobody.

internal/bundle/bundle.go

@@ -12,33 +12,49 @@ package bundle
 import (
 	_ "embed"
 	"errors"
+	"fmt"
 	"strings"
 
 	"github.com/novox/mesh-host/internal/declaration"
 )
 
-// substrate is the pinned tier-1 descriptor, appliable with no mesh present.
+// One bundle per operating system, because its CONTENTS are per system even though its
+// mechanism is not: package names, unit names and service names all differ
+// (novox/hq ADR 0060). All three are embedded and the host applies the one it was built for —
+// an arch host never reads the alpine bundle.
 //
-// A host built without one carries the placeholder below, and says so rather than applying
+// A host whose bundle is only comments carries nothing, and says so rather than applying
 // nothing and reporting success — a host that silently did nothing on a first node would look
 // exactly like one that worked.
 //
-//go:embed substrate.lock
-var substrate []byte
+//go:embed substrate-arch.lock
+var archLock []byte
 
-// ErrEmpty means this host was built without a bundle.
+//go:embed substrate-alpine.lock
+var alpineLock []byte
+
+//go:embed substrate-android.lock
+var androidLock []byte
+
+var locks = map[string][]byte{
+	"arch":    archLock,
+	"alpine":  alpineLock,
+	"android": androidLock,
+}
+
+// ErrEmpty means this host carries no bundle.
 var ErrEmpty = errors.New(
-	"this host carries no bundle. A host built without one cannot raise a first node, and " +
-		"applying nothing would look exactly like applying something")
+	"this host carries no bundle. A host without one cannot raise a first node, and applying " +
+		"nothing would look exactly like applying something")
 
 // Raw returns the carried bytes, for inspection.
-func Raw() []byte { return substrate }
+func Raw(system string) []byte { return locks[system] }
 
 // IsEmpty reports whether anything was built in. A bundle of only comments and whitespace is
-// empty for this purpose: the placeholder is a comment, and treating it as content would mean
-// a default build claims to carry a substrate.
-func IsEmpty() bool {
-	for _, line := range strings.Split(string(substrate), "\n") {
+// empty for this purpose: a placeholder is a comment, and treating it as content would mean a
+// host claims to carry a substrate it does not.
+func IsEmpty(system string) bool {
+	for _, line := range strings.Split(string(locks[system]), "\n") {
 		line = strings.TrimSpace(line)
 		if line != "" && !strings.HasPrefix(line, "//") {
 			return false
@@ -52,14 +68,17 @@ func IsEmpty() bool {
 // The same parser the link will use. A bundle that reaches a machine and is then refused by the
 // host that carries it would be a build-time mistake discovered at the worst possible moment,
 // which is why `mesh-host bundle` exists to ask before it matters.
-func Load() (*declaration.Declaration, error) {
-	if IsEmpty() {
+func Load(system string) (*declaration.Declaration, error) {
+	if _, known := locks[system]; !known {
+		return nil, fmt.Errorf("no bundle is built for %q", system)
+	}
+	if IsEmpty(system) {
 		return nil, ErrEmpty
 	}
 	// ParseTrusted: the bundle arrives with the binary, so it may carry actions the link may
 	// not (novox/hq ADR 0047). The bootstrap needs them — creating the control plane's database
 	// happens before there is any mesh to ask for one.
-	return declaration.ParseTrusted(stripComments(substrate))
+	return declaration.ParseTrusted(stripComments(locks[system]))
 }
 
 // stripComments removes whole-line `//` comments so a bundle can be annotated.

internal/bundle/bundle_test.go

@@ -15,10 +15,10 @@ func TestADefaultBuildCarriesNothingAndSaysSo(t *testing.T) {
 	// The important one. A host built without a bundle that applied nothing and reported
 	// success would look exactly like a host that raised a first node — and the difference
 	// would surface as a mesh that never came up, with nothing to point at.
-	if !IsEmpty() {
+	if !IsEmpty("arch") {
 		t.Fatal("the default build claims to carry a substrate")
 	}
-	_, err := Load()
+	_, err := Load("arch")
 	if !errors.Is(err, ErrEmpty) {
 		t.Fatalf("an empty bundle did not refuse: %v", err)
 	}
@@ -80,3 +80,34 @@ func TestWhatValidatesIsWhatIsApplied(t *testing.T) {
 func parseFor(raw []byte) (any, error) {
 	return declarationParse(stripComments(raw))
 }
+
+func TestEverySystemHasABundleAndAndroidsRefuses(t *testing.T) {
+	// The bundle's contents are per system even though its mechanism is not (novox/hq ADR
+	// 0060), so a host must find one built for it — and a host built for a system with no
+	// bundle at all must say that rather than behave like an empty one.
+	for _, system := range []string{"arch", "alpine", "android"} {
+		if _, err := Load(system); err == nil {
+			t.Errorf("%s: a placeholder bundle loaded as if it had contents", system)
+		} else if !errors.Is(err, ErrEmpty) {
+			t.Errorf("%s: refused for the wrong reason: %v", system, err)
+		}
+	}
+
+	if _, err := Load("debian"); err == nil {
+		t.Error("a bundle was loaded for a system nobody has built")
+	} else if errors.Is(err, ErrEmpty) {
+		t.Error("an unbuilt system was reported as an empty bundle; those are different things")
+	}
+}
+
+func TestAndroidsBundleSaysWhyThereIsNone(t *testing.T) {
+	// Not a placeholder waiting to be filled in. An android host implements neither `package`
+	// nor `container` nor `service`, so every step of the bootstrap is a shape it does not
+	// have — a partial host can JOIN a mesh and cannot BE the first node.
+	text := string(Raw("android"))
+	for _, want := range []string{"cannot raise a mesh", "JOIN", "first node"} {
+		if !strings.Contains(text, want) {
+			t.Errorf("the android bundle does not explain itself; missing %q", want)
+		}
+	}
+}

internal/bundle/substrate-alpine.lock

@@ -0,0 +1,11 @@
+// substrate-alpine.lock — the pinned tier-1 descriptor the ALPINE host carries.
+//
+// Per system, because its CONTENTS are: this one names apk packages and OpenRC services where
+// the arch bundle names pacman packages and systemd units (novox/hq ADR 0060).
+//
+// Empty on purpose. What belongs here is the closure for a one-node mesh, and that is not
+// yet known: novox/hq research 012 asks what the minimum actually is, and research 011 is
+// what would compute it rather than assert it.
+//
+// A host built with this placeholder refuses to reconcile and says why, rather than applying
+// nothing and reporting success. Building a real host means building it with a real bundle.

internal/bundle/substrate-android.lock

@@ -0,0 +1,12 @@
+// substrate-android.lock — deliberately not a bundle.
+//
+// An android host cannot raise a mesh, and this file says so rather than being an empty
+// placeholder waiting to be filled in.
+//
+// The substrate is a container runtime, a store and the control plane (novox/hq
+// 07-the-substrate.md). An android host implements `file`, `directory` and `action` and refuses
+// `package`, `container` and `service` (ADR 0060) — so every step of the bootstrap is a shape it
+// does not have. No amount of filling this in changes that.
+//
+// **A partial host can JOIN a mesh and cannot BE the first node.** That is a real distinction
+// and it belongs here, where somebody looking for the android bundle will find it.

internal/bundle/substrate-arch.lock

@@ -1,4 +1,7 @@
-// substrate.lock — the pinned tier-1 descriptor this host carries.
+// substrate-arch.lock — the pinned tier-1 descriptor the ARCH host carries.
+//
+// Per system, because its CONTENTS are: package names, unit names and service names all differ
+// (novox/hq ADR 0060). The mechanism is shared; what it names is not.
 //
 // Empty on purpose. What belongs here is the closure for a one-node mesh, and that is not
 // yet known: novox/hq research 012 asks what the minimum actually is, and research 011 is