## What changed
- Read `mcp_servers` configuration and requirements from each selected remote
executor and add eligible HTTP servers to the thread's MCP runtime.
- Bind discovered servers to the thread's concrete executor snapshot and apply
environment MCP policy and requirements. Discovery is best effort, and
executor-local servers are not treated as required at startup.
- Ignore unsupported stdio servers and HTTP configurations that depend on
environment-provided headers or header helpers.
## Testing
- Added an app-server integration test covering discovery, authenticated HTTP
tool invocation, requirements enforcement, and exclusion of stdio servers.
GitOrigin-RevId: 6e1cdcebdbb1cc21a5a2285fbc5617d8d5997182