Bumps model IDs across examples/*.yaml (and the gopher.hcl sibling) to the
current-generation anchors: Claude Sonnet 5 / Opus 5 (with Sonnet 4.6 / Opus
4.8 kept where a key signals a cheaper/fallback tier), GPT-5.6-sol/-terra,
Gemini 3.8 Flash, Grok 4.5, Kimi K3, and Llama 4 Maverick on OpenRouter.
Refs #4137.
Remove the leading '#!/usr/bin/env docker agent run' shebang and
following blank line from all example YAML and HCL files, as the
config format is now self-documenting.
Arnaud Héritier
David Gageot
Guillaume Tardif
Jean-Laurent de Morlhon