Add Admin runtime reasoning controls - #348

I reproduced a runtime-default mismatch on the current head (713e534). The web PUT /v1/runtime-config endpoint accepts Codex with effortLevel: "max", returns HTTP 200, and echoes "max" as the effective saved default. Resolving that same persisted selection through resolveRuntimeChoiceDurable() returns no effortLevel, so the UI reports a default that actual turns silently ignore.

Could this PR update the surface endpoint to validate with thinkingLevelsForHarness(harnessId) and gate fast mode with harnessSupportsFastMode(harnessId), matching the Admin endpoint and shared resolver? A focused regression test should verify that unsupported combinations such as Codex max are rejected rather than persisted.

Thanks for this, @16francej — and sorry for the slow response.

We're closing this PR. Per CONTRIBUTING.md, since coding agents write most of the underlying code now, we'd rather receive feature ideas as a short human-written note in adrs/ — informal is great, just the idea in your own words — and bugs as a plain issue. If we're aligned we're happy to burn our own tokens on the implementation, and we'll credit you as co-author.

We don't want your idea to get lost, so we've captured it in #797 to triage on our side. Please feel free to open an adrs/ note if you feel strongly about the approach. Appreciate you engaging with the repo!