docs: fold AGENTS.md into CLAUDE.md and record the backend traps

One agent doc per repo, and it is CLAUDE.md. Unlike elsewhere, the
existing CLAUDE.md was not a stub -- it carried seven hard-won gotchas,
all of which survive intact. AGENTS.md supplied the deployment and
release material, minus its feature-branch mandate and its `git add -A`
snippet, and minus its pointer to portainer-core, which is deprecated and
must not be used as a source of infra facts. README.md and
docs/philosophy.md linked to the retired file, so those pointers move
with it.

The new material is two traps that both make the runtime look like the
opposite of what it is.

A cold import inside the container loads src/anthropic but not
src/ollama, and Ollama is the primary backend. The only import of
src/ollama is a function-body one at src/anthropic/model_selector.py:230,
while PREFER_CLOUD_BACKEND=false keeps the Claude path off. Read the
module list naively and the disabled fallback looks live while the hot
path looks dead. This matters because the Claude migration is abandoned
and its remnants are supposed to read as vestigial, not as unfinished
work; the doc carries the decision id so that reasoning is fetchable.

Second, get_household_registry() in a fresh `docker exec python` returns
zero members while the running app serves two models from it. It is
populated at startup, so importing the singleton from outside the app and
reading it as empty is a measurement error, not a finding.

Co-Authored-By: Claude <noreply@anthropic.com>

README.md

@@ -406,7 +406,7 @@ tatlock/
 
 ## Development
 
-For LLM agent development guidelines and architectural decisions, see [AGENTS.md](AGENTS.md).
+For LLM agent development guidelines and architectural decisions, see [CLAUDE.md](CLAUDE.md).
 
 ## Contributing
 
@@ -420,7 +420,7 @@ For LLM agent development guidelines and architectural decisions, see [AGENTS.md
 
 - **System Philosophy**: [docs/philosophy.md](docs/philosophy.md) - Vision, goals, and architectural patterns
 - **Development Roadmap**: [docs/roadmap.md](docs/roadmap.md) - Open work and planned phases
-- **Developer Guidelines**: [AGENTS.md](AGENTS.md) - LLM agent development patterns
+- **Developer Guidelines**: [CLAUDE.md](CLAUDE.md) - LLM agent development patterns
 - **Version History**: [CHANGELOG.md](CHANGELOG.md) - Changes and releases
 
 ### External References