Genkit JS and CLI 1.40.0

What's Changed

• docs(js/genkit): add Agents section to README by @pavelgj in #5641
• chore(js/plugins/google-genai): remove shutdown veo models by @ifielker in #5680
• fix(agents)!: return not found for missing snapshots by @MichaelDoyle in #5715
• feat(js/testing): mockModel + echoModel for genkit/testing by @cabljac in #5475
• feat(js/plugins/anthropic): Support for Claude sonnet 5 by @ifielker in #5747
• fix(genkit-tools): prevent path traversal and bind to localhost by @pavelgj in #5751
• feat(js/plugins/vertexai/modelgarden): support for claude-sonnet-5 by @ifielker in #5721
• fix(js): serialize callable middleware functions in reflection v2 listValues by @MichaelDoyle in #5748
• feat(js/plugins/google-genai): Multi-region support by @ifielker in #5753
• fix(compat-oai): accumulate streamed tool-call arguments in chunks by @pavelgj in #5754

New Contributors

• @IzaakGough made their first contribution in #5648

Full Changelog: v1.39.0...v1.40.0