Local embedding provider (provider=local) is unreachable from config and startWarmup() is never called #678

Summary

createEmbeddingService() (src/core/store/embedding.ts) fully supports LocalEmbeddingService (node-llama-cpp + embeddinggemma-300m, offline, 768-dim), but two layers block it in practice:

1. config.ts rewrites provider=local to provider=none and sets embeddingEnabled=false: "Local embedding provider is not available in user config."
2. store/factory.ts (sqlite branch) only creates an embedding service when config.embedding.enabled && config.embedding.provider !== "local" && config.embedding.apiKey.

Additionally, after a local service is created, nothing ever calls startWarmup() — the GGUF model is never downloaded and embed() throws EmbeddingNotReadyError. Grep shows zero call sites for startWarmup outside the class itself.

Impact

Users who want fully-offline embedding (no external API key) cannot enable it via config; and if they force it, recall silently degrades because the model never loads.

Suggested fix

• Allow provider=local in config parsing (or expose an explicit enable flag),
• Create the service for provider=local in the sqlite store factory,
• Call embeddingService.startWarmup() once during core/gateway startup (it is a safe no-op for remote providers).

Verified on main @ 0.3.6 with Standalone Gateway (src/gateway/server.ts).