SessionState now carries the model a session launched with, and both
recovery constructors (mux recovery and reboot restore) pass it back, so a
recovered session relaunches on the same --model rather than the account
default. A top-level `model` sent with any other CLI is refused, since
those take their model in their own config object, and an empty string
means no per-session model, as it does for modelOverride.
CLAUDE.md now describes both routes for a Claude model. The tests pin
which of `model` and `modelOverride` reaches the launch and which the
case file, and that a model opening with a dash renders as --model's value.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>