Adds the vendor-agnostic seam the AI assistant + match-ranking plug into:
- LLMProvider / EmbeddingProvider ABCs (base.py). LLM and embeddings are
SEPARATE abstractions — Anthropic has no embeddings endpoint, so each is
configured independently and either can be off.
- NullLLMProvider / NullEmbeddingProvider — the default; fail loud with a clear
"not configured" error so AI-off deployments don't silently no-op.
- AnthropicLLMProvider — first concrete LLM impl, via the official anthropic SDK
(default model claude-opus-4-8). A local provider (e.g. Ollama) would be
another subclass of the same interface.
- Factory in deps.py (get_llm_provider / get_embedding_provider) selects by
env (MODEL_PROVIDER / EMBEDDING_PROVIDER); documented in .env.example.
Providers are read-only text/vector producers — they never touch the DB, so the
"AI never writes autonomously" invariant (CLAUDE.md #1) holds; writes will go
through ChangeProposal (#214).
Tests: provider selection (null default, anthropic when keyed, fallback without
key) + null providers raise. 81 passed.
Closes#215
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Justin Paul <justin@jpaul.me>
