`resolve_thinking` is exported, and its third argument turned from `bool`
into `Effort` this cycle — so the most natural downstream call now passes
the `"low"` it read out of JSON or config. Every gate inside compares by
identity, and `"none" is Effort.NONE` is always false: the tier was not
rejected, it was silently misjudged. Phase 2 read the on-form for a
request that wanted the off-form, Phase 4 was skipped entirely on a model
that cannot be disabled, and the only visible symptom arrived much later
as an AttributeError from `.value` — an exception that is neither
documented nor one of the four error classes.
Design 4.4 already lists this as the fourth entry a tier can come in
through; this makes the code agree with it.
iomgaa
4866e6b858