Lift the Ollama subprocess shell-out out of EmailDriver and into a
proper provider subpackage shape:
decnet/orchestrator/emailgen/llm/
base.py — LLMBackend Protocol + LLMResult + LLMTimeout
factory.py — get_llm() reads DECNET_EMAILGEN_LLM
impl/ollama.py — current 'ollama run' subprocess path
impl/fake.py — canned-output backend used by tests
Driver now takes an LLMBackend on construction (or inherits the
factory default). Tests inject FakeBackend instead of monkeypatching
the subprocess layer, which is cleaner and ~10x faster. Swapping
Ollama for the Anthropic API / vLLM / llama.cpp is now a third branch
in factory.py; no driver rewrite needed.
Mirrors the convention used by decnet.web.db.factory + decnet.bus.factory
per the provider-subpackages-from-day-one rule in memory.