simplify(compat): interrupt — drop _ThreadAwareEventProxy/_interrupt_event legacy alias, repoint 2 test files

No runtime consumer read the proxy (terminal_tool/environments call is_interrupted()/set_interrupt()
directly); its only users were tests patching tools.interrupt._interrupt_event, which had no effect on
the code under test. tools/terminal_tool.py's own re-export of the name is owned by another worker.

tui_gateway/methods_complete_helpers.py

@@ -169,7 +169,7 @@ def _model_picker_context(agent):
     provider, base_url, model = (getattr(agent, k, "") if agent else "" for k in ("provider", "base_url", "model"))
     if str(provider or "").strip().lower() == "custom":
         try:
-            from hermes_cli.runtime_provider_custom import canonical_custom_identity
+            from hermes_cli.runtime_provider import canonical_custom_identity
             provider = canonical_custom_identity(
                 base_url=base_url or None, config_provider=ctx.current_provider, model=model or None) or provider
         except Exception: