Adds two real-client tests on top of the salvaged #34783 fix:
- config-less custom:<name> endpoint routes via the carried live base_url
(guards the #34777 symptom directly, not just the wiring)
- named custom:<name> WITH a config entry still resolves via the
named-custom branch (regression guard against collapsing to bare custom)
When a user configures a custom: provider (e.g. custom:openclaw-router),
set_runtime_main() only stored provider and model in process-local globals.
_resolve_auto() then had no base_url or api_key for the custom endpoint,
causing Step 1 to fail and auxiliary tasks (approval, compression, title
generation) to fall through to the aggregator chain and route to wrong
providers.
Fix: extend set_runtime_main() to accept base_url, api_key, and api_mode
keyword arguments; store them in new globals alongside the existing provider
and model; fall back to these globals in _resolve_auto() when the main_runtime
dict is empty. The call site in conversation_loop.py now passes all five
fields from the agent object.
Fixes#34777
