feat(ollama): detect model capabilities dynamically via /api/show

[intel352]

Summary

Replace the hardcoded toolSupportedModels and mediaSupportedModels allowlists in the Ollama plugin with dynamic capability detection from Ollama's /api/show endpoint.

Problem

The Ollama plugin maintains static string arrays of model names that support tools and media. Newly released models (e.g. gemma4, which Ollama reports as tool-capable via its API) don't work with tool calling until someone manually updates these lists and ships a new Genkit release. This creates an unnecessary maintenance burden and blocks users from using new models with tools.

Solution

Ollama's POST /api/show endpoint returns a capabilities array (e.g. ["completion", "vision", "tools", "thinking"]) that accurately reports what each model supports. This PR queries that endpoint when determining model capabilities, falling back to the existing static lists when the server doesn't report capabilities (older Ollama versions).

Changes

• go/plugins/ollama/ollama.go:
  • Add getModelCapabilities() — queries /api/show for a model's capabilities
  • Add modelSupportsFromCapabilities() — derives ModelSupports from capability strings, with static-list fallback
  • Update DefineModel() to use dynamic detection when no explicit opts provided
  • Update ListActions() and ResolveAction() to use dynamic detection
• go/plugins/ollama/ollama_test.go:
  • Add TestGetModelCapabilities — mock server tests for tools/no-tools/unknown models
  • Add TestModelSupportsFromCapabilities — unit tests for dynamic and fallback paths

Backward Compatibility

• When /api/show returns capabilities → used directly (new behavior)
• When /api/show doesn't return capabilities or fails → falls back to existing static allowlists (existing behavior preserved)
• Explicit ModelOptions passed to DefineModel() are still respected (no change)

Testing

All existing tests pass. New tests cover:

• Capability detection from mock /api/show endpoint
• Fallback to static lists when no capabilities reported
• Models in the static list still work via fallback
• Unknown models default to no tools/media

🤖 Generated with Claude Code

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[gemini-code-assist]

Code Review

This pull request replaces hardcoded model capability allowlists with dynamic capability detection by querying the Ollama /api/show endpoint. This allows newly released models to work automatically without code changes. Feedback focuses on performance and reliability concerns regarding network I/O, specifically recommending the use of contexts with timeouts to prevent hanging requests, checking for context cancellation in loops, and avoiding I/O operations while holding mutexes to prevent resource contention.