refactor(web): rewrite webserver as a plain route-registration plugin

HttpServerService provides ctx.httpServer: register(route) -> disposer
(duplicate patterns throw), tapIndex transforms in registration order, and
the bound port; matching is exact > longest prefix > static dist fallback
(403/405/SPA semantics preserved). The server listens on activation, answers
per-request failures with 400 + a log line instead of exiting the process,
and knows no harness concepts — the boot graph, bundle routes, SSE channel,
and /api prefix all moved to their owning plugins.

packages/host/webserver/tsconfig.json

@@ -11,6 +11,9 @@
     {
       "path": "../../../vendor/cordis"
     },
+    {
+      "path": "../../../vendor/schemastery"
+    },
     {
       "path": "../../support/invariants"
     }