Drop the bespoke `merger.reviewerModel` setting. The AI merge reviewer now resolves its model via `resolveValidatorSettingsModel` — the same reviewer/validator lane used elsewhere (project validator → global validator → project default) — falling back to the merger model only if that lane is empty. Removes the setting from the type, schema default, and the Settings UI. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>