rename gateway-* → system-model-* + gateway-messaging, de-ollama, add system-model-explorer

- Rename gateway-provider → system-model-provider (generic :local provider, no hardcoded ollama)
- Rename gateway-llm → system-model (model-request dispatcher)
- Rename system-embedding-gateway → system-model-embedding
- Rename gateway-manager → gateway-messaging (public api renamed to messaging-*)
- Add system-model-explorer (model discovery via OpenRouter API, cached, per-slot recommendations)
- Fix skill loader export: replace prefix-matching with fbound/boundp-based export (20 skills now export)
- Add model-router to skill-loader exclusion list (loaded via CLI)
- De-ollama: remove hardcoded assumed-available patterns from provider pipeline
- Default cascade: cloud-only (openrouter, openai, groq, gemini, deepseek, nvidia, anthropic)
- Env example: add LOCAL_BASE_URL, fix cascade order
- All org files updated with architectural prose (literate programming)

README.org

@@ -49,7 +49,7 @@ See [[file:docs/USER_MANUAL.org][User Manual]] for the full guide.
 - [[file:org/core-memory.org][Memory]] — Single-address-space object store with Merkle-tree integrity and snapshot rollback
 - [[file:org/core-skills.org][Skill Engine]] — 20 hot-reloadable skills loaded at boot, each an independent Org file
 - [[file:org/gateway-tui.org][TUI]] — Croatoan-based terminal interface connected via framed TCP protocol
-- [[file:org/gateway-llm.org][LLM Routing]] — Cascade dispatch through multiple providers with tier-based model selection
+- [[file:org/system-model.org][LLM Dispatch]] — Central dispatch for model inference requests
 
 * Project Documentation