ADR 0041 and the build handoff for the node host

Building tier 0 forced the question "the one binary installed by hand" had been
carrying unexamined. A TypeScript host needs a runtime present before it runs,
so the thing installed by hand becomes two — and the second must be installed by
the means the host exists to replace.

So the host is a statically linked binary that requires nothing present, written
in Go. Rejected: a runtime installed first, which breaks the property the tier
rests on; and bundling the runtime into the executable, which carries ninety
megabytes to preserve a language choice and puts a young feature at the bottom
of the stack.

The argument that decided it is architectural rather than about taste. 0037
means the host never queries the mesh database and 0039 means it only receives
declarations, so the host shares NO code with any other tier — not a client, not
a schema, not the SDK. The language boundary falls exactly on a boundary that
already exists, and a second language usually costs duplicated logic where here
there is none to duplicate.

§8 gains a scope: it said "TypeScript throughout" when everything was a service
or a surface, and is now scoped to those with tier 0 named. Another sync owed.

Playbook 04 steps 2 and 4: repos.md records mesh-host as existing, the design
takes code: [mesh-host] and status: in-progress.

00-META/how-we-build.md

@@ -268,6 +268,10 @@ Data access, business logic and the interface layer are separate.
 
 ### Types
 
+*Scope: the mesh's services and surfaces. Tier 0 is a statically linked binary that must depend
+on nothing installed first, and is written in Go —
+[ADR 0041](../02-DECISIONS/0041-the-host-depends-on-nothing.md).*
+
 - TypeScript throughout; no new untyped JavaScript.
 - Strict, with no implicit `any` and no unchecked index access.
 - Public functions state their return type. Prefer `unknown` with a guard over `any`. Errors

00-META/repos.md

@@ -21,13 +21,13 @@ and a forge address is an operational detail (see [`README`](../README.md)).
 ## What the mesh becomes
 
 [ADR 0030](../02-DECISIONS/0030-the-repository-structure.md) records the repositories the
-monorepo decomposes into. **Only `mesh-lab` exists so far** — it is built first
+monorepo decomposes into. **`mesh-lab` and `mesh-host` exist so far** — the lab is built first
 ([ADR 0029](../02-DECISIONS/0029-the-labs-first-scenario-has-no-pipeline.md)); the rest are the
 target, not the present.
 
 | Repository | Tier | Holds |
 |---|---|---|
-| `mesh-host` | 0 | the node host — the one binary installed by hand |
+| `mesh-host` | 0 | **exists.** The node host — one statically linked binary, requiring nothing present ([ADR 0041](../02-DECISIONS/0041-the-host-depends-on-nothing.md)) |
 | `mesh-substrate` | 1 | the four pinned services, as declarations |
 | `mesh-control` | 2 | the control plane and its contexts |
 | `mesh-surfaces` | 3 | tools, web, cli |