Add local Ollama model selection to the web composer

[Wachynaky]

Expose locally-installed Ollama models as selectable chat models in the composer's model picker. The Claude Agent SDK only speaks the Anthropic Messages API, so Ollama (OpenAI-compatible) is reached through the bundled CLIProxyAPI proxy, registered as an openai-compatibility upstream — this requires proxy.enabled.

Backend:

• OllamaConfig + ollama_routable gate (Ollama enabled AND proxy enabled)
• nerve/ollama.py: best-effort model discovery via Ollama GET /api/tags
• proxy/service.py: register discovered models as a proxy upstream
• GET /api/models route for the picker
• engine: thread per-session model, recreate the SDK client on a mid-session model switch, and suppress Anthropic-only knobs (extended thinking, effort, context-1m beta) for non-Claude models
• server: pass the WS per-message model through to run()
• startup warning when ollama.enabled but proxy.enabled is false

Frontend:

• api.getModels() + optional model arg on ws.sendMessage
• chatStore holds available/selected/default model (persisted to localStorage)
• ChatInput renders a model picker, shown only when more than one model is offered

config.example.yaml: document the proxy and ollama blocks.

[Wachynaky]

Sorry, I guess this isn’t the right way or the right code for this feature, but I was doing it locally and in the end the Nerve agent uploaded it itself, with my help running the Git commands!