Summary

• log list_picker_providers exceptions in the gateway /model interactive picker path before falling back to the text list
• keep the existing fallback behavior unchanged for Telegram/Discord users
• add a regression test that forces the picker provider loader to raise and verifies the warning plus text fallback

Context

Closes #20966.

Current main already accepts the current_base_url and current_model kwargs in list_picker_providers and has coverage for that passthrough. This PR addresses the remaining silent-failure part of the issue: if the picker provider loader regresses again, the gateway no longer drops into the text list with no diagnostic trail.

Verification

scripts/run_tests.sh tests/gateway/test_model_command_custom_providers.py tests/hermes_cli/test_list_picker_providers.py

Result: 12 passed, 3 warnings.