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-delta.py

@@ -0,0 +1,29 @@
+#!/usr/bin/env python3
+# A tools bundle in a second language (novox/hq ADR 0187): MCP over stdio, no SDK, no dependencies.
+# One tool of its own, one seat verb, and one that exits the process mid-call.
+import json, sys
+
+def say(m):
+    m["jsonrpc"] = "2.0"; sys.stdout.write(json.dumps(m) + "\n"); sys.stdout.flush()
+
+TOOLS = [
+    {"name": "greet", "description": "say hello", "inputSchema": {"type": "object", "properties": {"who": {"type": "string"}}}},
+    {"name": "node-lamp.on", "description": "the seat's verb", "inputSchema": {"type": "object", "properties": {}}},
+    {"name": "die", "description": "exit without answering", "inputSchema": {"type": "object", "properties": {}}},
+]
+for line in sys.stdin:
+    req = json.loads(line); rid = req.get("id"); m = req.get("method"); p = req.get("params") or {}
+    if m == "initialize":
+        say({"id": rid, "result": {"protocolVersion": "2025-03-26", "capabilities": {"tools": {}}, "serverInfo": {"name": "delta", "version": "1"}}})
+    elif m == "tools/list":
+        say({"id": rid, "result": {"tools": TOOLS}})
+    elif m == "tools/call":
+        name = p.get("name"); args = p.get("arguments") or {}
+        if name == "greet":
+            say({"id": rid, "result": {"content": [{"type": "text", "text": json.dumps({"greeting": "hello " + args.get("who", "world"), "language": "python"})}]}})
+        elif name == "node-lamp.on":
+            say({"id": rid, "result": {"content": [{"type": "text", "text": json.dumps({"on": True, "language": "python"})}]}})
+        elif name == "die":
+            print("delta: told to die", file=sys.stderr); sys.exit(3)
+        else:
+            say({"id": rid, "error": {"code": -32602, "message": "no such tool"}})