refactor(web): upgrade apiproxy to the api-gateway service plugin

createApiProxy moves from dsh-host-runtime into dsh-host-apiproxy (the
dependency direction already pointed this way); the package now
default-exports ApiProxyService (config {provider, model}, provides
ctx.apiProxy) while staying transport-agnostic — it registers no routes.
Runtime keeps bootHost/startHost for the headless path with its import
re-anchored, and drops the mountWebPlugins roster mounting helper.

packages/host/apiproxy/tsconfig.json

@@ -8,18 +8,33 @@
     "src"
   ],
   "references": [
+    {
+      "path": "../../../vendor/cordis"
+    },
+    {
+      "path": "../../../vendor/schemastery"
+    },
     {
       "path": "../../util/brand"
     },
     {
       "path": "../../llm/llm"
     },
+    {
+      "path": "../../core/agent"
+    },
     {
       "path": "../../core/session"
     },
     {
       "path": "../../core/tools"
     },
+    {
+      "path": "../../session-persistence/session-persistence"
+    },
+    {
+      "path": "../../session-title/session-title"
+    },
     {
       "path": "../../ui/user-approval"
     },