feat: make /reasoning session-scoped by default

[Alex-giao]

Summary

• make /reasoning <level> session-scoped by default in CLI and gateway
• add --global to persist reasoning changes to config.yaml
• thread session-scoped reasoning overrides through gateway background/helper flows and reset cleanup
• teach TUI config + slash status paths to respect the active session override
• add regression coverage for CLI, gateway, background routing, reset cleanup, and TUI behavior

Test Plan

• scripts/run_tests.sh tests/cli/test_reasoning_command.py tests/gateway/test_reasoning_command.py tests/gateway/test_session_model_reset.py tests/gateway/test_session_model_override_routing.py tests/test_tui_gateway_server.py
• scripts/run_tests.sh tests/gateway/test_background_command.py tests/gateway/test_session_model_override_routing.py
• git diff --check

Notes

• I also attempted the full scripts/run_tests.sh suite in this environment, but it surfaced unrelated existing failures outside the touched areas before completion, so the verification above focuses on the directly impacted paths.

[teknium1]

Closing as superseded by #15533.

Triage notes (high confidence):
Session-scoped /reasoning is already on main in gateway/run.py:2773 (_set_session_reasoning_override) and merged via PR #15533 (2026-04-26) 'fix(gateway): make /reasoning session-scoped by default'.

Thanks for the contribution — the underlying problem this PR addresses has been resolved by the linked PR on current main. If you believe this was closed in error, please comment and we'll reopen.

(Bulk-closed during a CLI PR triage sweep.)

[jussihuotari]

It seems to me that this was closed in error.

• It seems that in gateway the reasoning is session-scoped. Re: _handle_reasoning_command in https://github.com/NousResearch/hermes-agent/blob/main/gateway/slash_commands.py#L1837
• But in CLI the reasoning is saved to config file as global setting: https://github.com/NousResearch/hermes-agent/blob/main/hermes_cli/cli_commands_mixin.py#L2001 . This is part of the original issue above, and also Feature: Session-only reasoning effort override via /reasoning command #9586