Reasoning effort was already available, but not expressed into the help
text, so it was non-discoverable.
Other issues discovered, but will fix in separate PR since they are
larger:
* #816 reasoningEffort isn't displayed in the terminal-header, making it
rather hard to see the state of configuration
* I don't think the config file setting works, as the CLI option always
"wins" and overwrites it
fcc76cf3e7