feat(go/plugins/vertexai): Add flows for Claude Sonnet 4.6 and Claude Opus 4.6 models in Vertex Model Garden

[cabljac]

Summary

• Adds Vertex Model Garden model registrations in Go for:

  • claude-sonnet-4-6
  • claude-opus-4-6

• Updates go/samples/basic/main.go to include explicit demo flows for both new models:

  • claudeSonnet46VertexModelGardenFlow

• claudeOpus46VertexModelGardenFlow

• Configures Anthropic request options in sample flows (MaxTokens) so Model Garden requests are valid.

Test plan

• gofmt on changed Go files

• go test ./plugins/vertexai/modelgarden ./samples/basic/...

• Verified Dev UI reflection includes:

  • /model/vertexai/claude-sonnet-4-6
  • /model/vertexai/claude-opus-4-6
  • /flow/claudeSonnet46VertexModelGardenFlow
  • /flow/claudeOpus46VertexModelGardenFlow

• Manual flow execution:

• Sonnet 4.6 success

Checklist

• PR title follows Conventional Commits
• Tested (manual + package tests)
• Docs updated (not required for this code-only change)

Closes #136
Closes #137

[gemini-code-assist]

Code Review

This pull request adds support for Claude Sonnet 4.6 and Claude Opus 4.6 models to the Vertex AI Model Garden plugin and includes sample flows demonstrating their usage. Feedback was provided regarding the naming consistency of the model labels to ensure they align with existing patterns in the codebase.

[gemini-code-assist]

The labels for the new models are inconsistent with the naming convention used for other versioned models in this file (e.g., lines 61, 65, 69). Those follow the pattern Claude [Version] [ModelName] (e.g., Claude 4.5 Sonnet), while these use Claude [ModelName] [Version]. Furthermore, the model IDs claude-sonnet-4-6 and claude-opus-4-6 lack the date suffix (e.g., -YYYYMMDD) present in all other models in this list, which is inconsistent and may cause runtime issues if the Vertex AI endpoint expects a fully qualified versioned ID.

Suggested change

	"claude-sonnet-4-6": {
	Label: "Claude Sonnet 4.6",
	Supports: &internal.Multimodal,
	},
	"claude-opus-4-6": {
	Label: "Claude Opus 4.6",
	Supports: &internal.Multimodal,
	},
	"claude-sonnet-4-6": {
	Label: "Claude 4.6 Sonnet",
	Supports: &internal.Multimodal,
	},
	"claude-opus-4-6": {
	Label: "Claude 4.6 Opus",
	Supports: &internal.Multimodal,
	},

[cabljac]

the model IDs are correct already i believe. the naming could be fixed though

[andyma-star]

Fixed — updated labels to Claude 4.6 Sonnet and Claude 4.6 Opus to match existing convention.

[apascal07]

Please put these in a separate sample. The basic- and intermediate- samples are meant to be canonical framework examples, not kitchen sinks. They can be a complete copy if need be, called anthropic-basic or similar.

[andyma-star]

Done — moved the Claude 4.6 flows out of go/samples/basic/main.go into go/samples/modelgarden/main.go so basic stays canonical.

[apascal07]

Can you make sure the anthropic plugin is updated too if needed?

[andyma-star]

Checked — I think no Anthropic plugin changes were needed for this PR. the required updates were in Vertex Model Garden model registration/sample usage.