refactor(plugins/google-genai): migrate to v2 API

[CorieW]

Checklist (if applicable):

• Tested (manually, unit tested, etc.)

[cabljac]

Suggested change

	// For conditional types in index.ts model
	// For conditional types in index.ts createModelRef

maybe i think

[Copilot]

Pull Request Overview

This PR migrates the Google Genkit plugin from the v1 to v2 API, refactoring how models, embedders, and background models are defined and managed. The migration simplifies the plugin architecture by removing the explicit Genkit instance parameter and transitioning to a more functional approach.

• Rename model() functions to createModelRef() for consistency
• Migrate from v1 plugin architecture to v2 with updated initialization and resolution patterns
• Update function signatures to remove Genkit instance parameters and return action objects directly

Reviewed Changes

Copilot reviewed 22 out of 22 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
js/plugins/google-genai/tests/vertexai/veo_test.ts	Update test mocks and function calls for v2 API migration
js/plugins/google-genai/tests/vertexai/lyria_test.ts	Replace model() calls with createModelRef() and update defineModel calls
js/plugins/google-genai/tests/vertexai/index_test.ts	Update test assertions and function calls for v2 API changes
js/plugins/google-genai/tests/vertexai/imagen_test.ts	Replace model function references and update defineModel signature
js/plugins/google-genai/tests/vertexai/gemini_test.ts	Update createModelRef calls and remove Genkit parameter from defineModel
js/plugins/google-genai/tests/vertexai/embedder_test.ts	Update defineEmbedder calls to remove Genkit parameter
js/plugins/google-genai/tests/googleai/veo_test.ts	Replace model() with createModelRef() and update test setup
js/plugins/google-genai/tests/googleai/index_test.ts	Update test structure for v2 plugin API and function renaming
js/plugins/google-genai/tests/googleai/imagen_test.ts	Replace model calls with createModelRef and update defineModel signature
js/plugins/google-genai/tests/googleai/gemini_test.ts	Update function calls and remove Genkit parameters from model definitions
js/plugins/google-genai/tests/googleai/embedder_test.ts	Update embedder definition calls to remove Genkit parameter
js/plugins/google-genai/src/vertexai/veo.ts	Implement v2 API with createModelRef and backgroundModel functions
js/plugins/google-genai/src/vertexai/lyria.ts	Migrate to v2 API removing Genkit parameter and using model function
js/plugins/google-genai/src/vertexai/index.ts	Complete plugin migration to v2 architecture with new init/resolve pattern
js/plugins/google-genai/src/vertexai/imagen.ts	Update to v2 API with createModelRef and model function
js/plugins/google-genai/src/vertexai/gemini.ts	Migrate gemini models to v2 API and remove Genkit parameters
js/plugins/google-genai/src/vertexai/embedder.ts	Update embedder implementation for v2 API with new function signatures
js/plugins/google-genai/src/googleai/veo.ts	Implement v2 changes with createModelRef and backgroundModel
js/plugins/google-genai/src/googleai/index.ts	Complete googleAI plugin migration to v2 architecture
js/plugins/google-genai/src/googleai/imagen.ts	Update imagen models to v2 API pattern
js/plugins/google-genai/src/googleai/gemini.ts	Migrate gemini implementation to v2 API structure
js/plugins/google-genai/src/googleai/embedder.ts	Update embedder for v2 API with new function signatures

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[Copilot]

Avoid using as any type assertion. Consider creating a proper stub interface or using more specific typing for the backgroundModel stub to maintain type safety.

Suggested change

	backgroundModelStub = sinon.stub(backgroundModel as any);
	backgroundModelStub = sinon.stub<typeof backgroundModel>(backgroundModel);

[Copilot]

Avoid using as any type assertion. Consider creating a proper stub interface or using more specific typing for the backgroundModel stub to maintain type safety.

[cabljac]

Can we avoid introducing an explicit any

[cabljac]

lgtm, make sure to test in dev UI to ensure we're not changing the display names of anything (same goes for all model plugin migrations)

[cabljac]

generally lgtm - one comment about an any we've introduced, would rather not.