fix(todotools): stop forcing the first-turn todo on models that refuse it (fixes #2218)

supportsNamedToolChoice returned true for every openai-completions and
openai-responses model. It now honours compat.supportsForcedToolChoice
(accepted by the models.json schema) and returns false for a model the
adapters remembered as refusing a forced choice, so later sessions on that
model send the reminder only.

Fixes #2202