feat(llm): add LLM integration module with OpenRouter and Claude Code adapters

Implements markitect/llm/ package with concrete LLMAdapter implementations:
- OpenRouterAdapter: HTTP via urllib with retry/backoff on 429/5xx
- ClaudeCodeAdapter: subprocess-based Claude CLI with stdin piping
- Factory pattern: create_adapter("openrouter") or create_adapter("claude-code")
- API key resolution chain: constructor > env var > project-root key file
- 42 unit tests, 2 integration tests (gated on API key / CLI availability)

Also adds the infospace-with-history example with Wealth of Nations VSM
analysis pipeline, templates, schemas, source chapters, and processed
output for chapters 1-2. process_chapters.py now supports --provider
and --model flags for automatic LLM-driven processing.

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

tests/unit/llm/test_factory.py

@@ -0,0 +1,33 @@
+"""Tests for markitect.llm.factory."""
+
+import pytest
+
+from markitect.llm.factory import create_adapter
+from markitect.llm.openrouter import OpenRouterAdapter
+from markitect.llm.claude_code import ClaudeCodeAdapter
+from markitect.llm.exceptions import LLMConfigurationError
+
+
+class TestCreateAdapter:
+    def test_openrouter(self):
+        adapter = create_adapter("openrouter", api_key="sk-test")
+        assert isinstance(adapter, OpenRouterAdapter)
+
+    def test_claude_code(self):
+        adapter = create_adapter("claude-code")
+        assert isinstance(adapter, ClaudeCodeAdapter)
+
+    def test_unknown_provider(self):
+        with pytest.raises(LLMConfigurationError) as exc_info:
+            create_adapter("unknown-provider")
+        assert "unknown-provider" in str(exc_info.value)
+
+    def test_model_passed_through(self):
+        adapter = create_adapter("claude-code", model="opus")
+        assert adapter._model == "opus"
+
+    def test_openrouter_system_prompt(self):
+        adapter = create_adapter(
+            "openrouter", api_key="sk-test", system_prompt="Be helpful"
+        )
+        assert adapter._system_prompt == "Be helpful"