feat(sse): discover Anthropic partner models on Vertex AI

[maci0]

Summary

• Add dynamic discovery of Anthropic/Claude models on Vertex AI via the Model Garden publisher endpoint (/v1/publishers/anthropic/models), using project-scoped URLs when a Service Account JSON credential is available
• Add targetFormat: "claude" heuristic in getModelTargetFormat so dynamically discovered Claude models on vertex/vertex-partner are correctly routed through the Anthropic Messages translator instead of Gemini
• Tag all static Claude model entries with targetFormat: "claude" and expand both vertex and vertex-partner registries with the current Claude model catalog

Motivation

Vertex AI model discovery only queried the Gemini Generative Language API (generativelanguage.googleapis.com/v1beta/models), so Claude models available through Vertex AI as Anthropic partner models were never discovered. The executor already handled Claude execution correctly via rawPredict, but without discovery the models didn't appear in the dashboard catalog unless manually added.

Changes

File	What
src/lib/providerModels/vertexAnthropicModelsParser.ts	New parser for Model Garden publisher response; handles both global and project-scoped resource name formats
src/app/api/providers/[id]/models/route.ts	Best-effort Anthropic discovery after Gemini discovery (Bearer auth only); extracts project_id from SA JSON for project-scoped endpoint
open-sse/config/providerModels.ts	getModelTargetFormat heuristic: claude-* on vertex/vp returns "claude" so response translation works for models not in the static list
open-sse/config/providers/registry/vertex/index.ts	Expanded static Claude list with targetFormat: "claude"
open-sse/config/providers/registry/vertex/partner/index.ts	Same treatment for vertex-partner

Test plan

• Configure a Vertex AI connection with a Service Account JSON credential
• Hit /api/providers/{vertex-id}/models and verify Claude models appear in the response alongside Gemini models
• Send a chat completion request to a discovered Claude model through the vertex provider and verify the response translates correctly
• Verify Express API key connections still discover Gemini models (Anthropic discovery is skipped, best-effort)
• Verify a Claude model NOT in the static registry (e.g. a future model) gets targetFormat: "claude" via the heuristic