A bundle that is not JavaScript is launched and spoken to over MCP on stdio (hq ADR 0187, to-be 38 WP1b)

The runtime imported a bundle into its own process, which only JavaScript can be. Now an entrypoint
that is not a plain JavaScript file — or is one marked executable — is started as a child with the
runtime's environment and asked `tools/list` once and `tools/call` per call; what it lists is
registered exactly as an imported bundle's registrations are, a `<seat>.<verb>` name as the seat's
implementation. So a tools bundle may be in any language, and the mesh's part — the subjects, the
seats, the `tools` answer, a failed bundle named — stays in the runtime and is shared by all of
them. A child that exits mid-call tells the caller so and is started again on its next call.

Proven against a real bus beside the three bundles already there: a Python bundle with no SDK at
all answers its tool and its seat verb; a TypeScript bundle written against the protocol and marked
executable is served through the launcher, shortcut off; a bundle told to exit is relaunched.

test/fixtures/many-epsilon.mjs

@@ -0,0 +1,8 @@
+#!/usr/bin/env node
+// A TypeScript bundle written against the protocol and marked executable: served through the
+// launcher like any other language, with the in-process shortcut off (novox/hq ADR 0187).
+import { serveStdio } from "@novox/mesh-sdk/stdio";
+
+await serveStdio("epsilon", [
+  { name: "seven", description: "epsilon's", input: {}, run: async () => ({ epsilon: 7, via: "stdio" }) },
+]);