feat: initial llm-connect package scaffold

Copy markitect.llm module into standalone llm_connect package.
All markitect.* imports replaced with llm_connect.* equivalents.
LLMError base class inlined (no markitect.exceptions dependency).
Verified: from llm_connect import create_adapter works.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

llm_connect/factory.py

@@ -0,0 +1,60 @@
+"""
+Factory for creating LLM adapters by provider name.
+"""
+
+from typing import Optional, Dict, Any
+
+from llm_connect.adapter import LLMAdapter
+from llm_connect.exceptions import LLMConfigurationError
+
+# Lazy imports to avoid pulling in every adapter at module load time.
+_PROVIDERS: Dict[str, str] = {
+    "openrouter": "llm_connect.openrouter.OpenRouterAdapter",
+    "claude-code": "llm_connect.claude_code.ClaudeCodeAdapter",
+    "gemini": "llm_connect.gemini.GeminiAdapter",
+    "openai": "llm_connect.openai.OpenAIAdapter",
+}
+
+
+def create_adapter(
+    provider: str = "openrouter",
+    model: Optional[str] = None,
+    api_key: Optional[str] = None,
+    system_prompt: Optional[str] = None,
+    **kwargs: Any,
+) -> LLMAdapter:
+    """Instantiate an :class:`LLMAdapter` for the given *provider*.
+
+    Args:
+        provider: ``"openrouter"``, ``"claude-code"``, ``"gemini"``, or ``"openai"``.
+        model: Model name (passed to the adapter constructor).
+        api_key: Explicit API key (OpenRouter / Gemini / OpenAI).
+        system_prompt: Optional system prompt (OpenRouter / Gemini / OpenAI).
+        **kwargs: Extra keyword arguments forwarded to the adapter.
+
+    Returns:
+        A ready-to-use :class:`LLMAdapter` instance.
+
+    Raises:
+        LLMConfigurationError: If *provider* is not recognised.
+    """
+    if provider not in _PROVIDERS:
+        known = ", ".join(sorted(_PROVIDERS))
+        raise LLMConfigurationError(
+            f"Unknown LLM provider {provider!r}. Choose from: {known}",
+            context={"provider": provider},
+        )
+
+    # Lazy import
+    fqn = _PROVIDERS[provider]
+    module_path, class_name = fqn.rsplit(".", 1)
+    import importlib
+    mod = importlib.import_module(module_path)
+    cls = getattr(mod, class_name)
+
+    if provider in ("openrouter", "gemini", "openai"):
+        return cls(model=model, api_key=api_key, system_prompt=system_prompt, **kwargs)
+    elif provider == "claude-code":
+        return cls(model=model, **kwargs)
+    else:
+        return cls(**kwargs)  # pragma: no cover