Correct the record: a limitation that no longer exists, and one that was never written

The connectivity design still said a hub cannot be filtered — a gap recorded in
the morning and closed in the afternoon, left standing as though it were
current. Worse than a stale date: it would send somebody away from something
that works.

`restart-on` was described nowhere, including the part added today that lets a
service reflect a file another module put on the machine. A rule the host
enforces and no document mentions is a rule nobody can rely on.

And nine of fifteen design documents claimed an `updated:` older than their last
change, some by a week. That field is what cross-cutting views are generated
from, so it is not decoration.

03-DESIGN/01-to-be/07-the-substrate.md

@@ -5,7 +5,7 @@ code:
   - mesh-host examples/substrate-first-node.lock
   - mesh-host internal/apply
   - mesh-lab test/integration/mesh.test.ts (a bare machine becomes a mesh)
-updated: 2026-08-30
+updated: 2026-08-31
 decisions:
   - 02-DECISIONS/0004-a-node-and-how-it-joins.md
   - 02-DECISIONS/0005-the-node-host.md