feat(providers): add native options and exact MCP grants (#3025)

* feat(providers): add native options and exact MCP grants

Keep provider policy in provider-owned schemas so unattended Hub runs can grant only requested tools from injected MCP servers. Preserve the native resolved sandbox policy when a workflow override is present, including configured writable roots.

* test(hub): verify real provider tool policy

* test(app): avoid pinning transient restart status

packages/app/e2e/browser/provider-subagents.real.spec.ts

@@ -34,7 +34,7 @@ const cases: ProviderSubagentCase[] = [
     provider: "codex",
     sentinel: "CODEX_CHILD_SENTINEL",
     expectedName: "Sentinel child",
-    providerConfig: { extra: { codex: { features: { multi_agent_v2: true } } } },
+    providerConfig: { providerOptions: { features: { multi_agent_v2: true } } },
     prompt:
       'Use the native collaboration.spawn_agent tool exactly once with task_name "sentinel_child" and fork_turns "none". Ask it to reply with exactly CODEX_CHILD_SENTINEL and do nothing else. Wait for it with collaboration.wait_agent, then reply ROOT_DONE. Do not use Paseo tools.',
   },