UI - Agent Settings route renders blank

[PetrBulanek]

Pre-requisities

• I am using the newest version of the platform (agentstack version shows that CLI and platform are the same version, and there is no newer version available)

Describe the bug
On route /agent/<providerId>/settings (page file: apps/agentstack-ui/src/app/(main)/agent/[providerId]/settings/page.tsx), settings components do not render (blank content area; no "Agent settings" header, no secrets section).

To Reproduce
Steps to reproduce the behavior:

1. Go to an agent route, e.g. /agent/<providerId>
2. Click the top-right agent menu (AgentNav) and select Settings
3. Confirm URL is /agent/<providerId>/settings
4. See blank page content (settings components are not rendered)

Expected behavior
AgentSettingsView should render the Settings UI (ViewHeader + Secrets section), or at least show a loading/error state instead of returning null.

Additional context
Root cause is very likely missing context initialization in settings flow:
PlatformContextProvider has no contextId on settings route, so token/client queries stay disabled, agentClient is never created, and A2AClientProvider short-circuits to null, preventing rendering of child components.