docs: bump claude-opus-4-6 to claude-opus-4-7 across docs, examples, and AGENTS.md

Syncs the README translations, CONTRIBUTING, docs/reference,
docs/guide, docs/examples JSONC configs, and the hierarchical
src/**/AGENTS.md files with the model version bump already landed
in the source and migration commits.

CONTRIBUTING.md

@@ -183,7 +183,7 @@ import type { AgentConfig } from "./types";
 
 export const myAgent: AgentConfig = {
   name: "my-agent",
-  model: "anthropic/claude-opus-4-6",
+  model: "anthropic/claude-opus-4-7",
   description: "Description of what this agent does",
   prompt: `Your agent's system prompt here`,
   temperature: 0.1,