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/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.