Backend half of the per-task effort control, on today's layout: POST /api/model/set
distinguishes omitted (leave the task's override alone) from explicit null (clear →
inherit) via model_fields_set, canonicalises a level through parse_reasoning_effort
(400 on an unknown one), and "Reset all to main" also drops every override. GET
/api/model/auxiliary returns reasoning_effort per task and the row summary shows it.
The inherit row reads "inherit · main model effort" (own i18n key in all six locales)
rather than reusing the provider's "auto · use main model" copy — the two mean
different things and the reused string read as "use the main model" for the effort.
Runtime already consumes auxiliary.<task>.reasoning_effort (agent/auxiliary_client.py)
and hermes model writes the same key (#110346), so Desktop and CLI now edit one value.
Closes#89259. Salvages #90649 by @higgs1729.