Add isolated conversational development runtime

[DevHabito]

What changed

• pre-registers E044 before implementation
• adds an isolated conversational runtime outside the frozen E043 desktop runtime
• requires explicit backend and model selection with no cross-provider fallback
• adds an OpenAI Responses adapter with mandatory model probing, store: false, strict Structured Outputs, no tools, and no provider-side continuation id
• performs model-backed UNDERSTAND followed by deterministic policy processing and model-backed EXPRESS
• keeps at most 60 temporary messages in memory and clears them on close
• exposes no persistent-memory, goal, RZS, sigma, identity, world-model, consent, capability, or action mutation handle
• adds an explicitly supplied local-backend seam without installing or discovering a local server
• adds a terminal command and an English setup guide

Why

Darwin needs an open-ended conversational development surface without turning the language model into the cognitive authority or contaminating the PURE E043 candidate. The protocol and implementation state explicitly that this remains an LLM-centered adapter, not evidence of consciousness, general cognition, or a Diana-like entity.

Validation

• E044 protocol committed first: 61d6f97
• implementation commit: ca04a2c
• 24/24 focused E044 tests passed
• full suite: 472 discovered, 471 executed and passed, 1 pre-existing Windows symlink skip, 0 failures
• E043 runtime SHA-256 unchanged: fd0d8aaf2bd1011addea581eaef172ce940157164dc013681d5326476d49f7e8
• E043 protocol SHA-256 unchanged: beea70ce6bcfd177a18d36feca016f5f93ed0bed7743fc73c31152cc19eaefad
• captured request tests verify configured model, store: false, strict schemas, and absence of tools and previous_response_id
• no live API or local-model call was made

Evidence ceiling

The OpenAI key and an explicit local backend were both unavailable on the test machine. Live model probing, live UNDERSTAND, live EXPRESS, the 20-30 minute conversation probe, language quality, and topic-return quality remain UNEXECUTED or UNKNOWN. E041/E042 remain independently blocked on human annotation.

This is a stacked draft PR targeting codex/v50-kernel-foundation so its diff contains only E044.