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>

markitect/llm/claude_code.py

@@ -0,0 +1,94 @@
+"""
+Claude Code CLI adapter — runs the ``claude`` CLI as a subprocess.
+"""
+
+import subprocess
+from typing import Optional
+
+from markitect.prompts.execution.llm_adapter import LLMAdapter
+from markitect.prompts.execution.models import RunConfig, LLMResponse
+from markitect.llm.config import LLMConfig
+from markitect.llm._token_estimator import estimate_tokens
+from markitect.llm.exceptions import (
+    LLMSubprocessError,
+    LLMTimeoutError,
+)
+
+
+class ClaudeCodeAdapter(LLMAdapter):
+    """LLM adapter that shells out to the ``claude`` CLI with ``--print``.
+
+    The compiled prompt is piped via **stdin** to avoid shell argument
+    length limits (compiled prompts can exceed 30 KB).
+    """
+
+    def __init__(
+        self,
+        cli_path: str = "claude",
+        model: Optional[str] = None,
+        config: Optional[LLMConfig] = None,
+    ):
+        self._config = config or LLMConfig(provider="claude-code")
+        self._cli_path = cli_path or self._config.claude_cli_path
+        self._model = model
+
+    # ── LLMAdapter interface ────────────────────────────────────────
+
+    def execute_prompt(self, prompt: str, config: RunConfig) -> LLMResponse:
+        cmd = [self._cli_path, "--print"]
+        if self._model:
+            cmd.extend(["--model", self._model])
+
+        timeout = config.timeout_seconds or self._config.timeout_seconds
+
+        try:
+            result = subprocess.run(
+                cmd,
+                input=prompt,
+                capture_output=True,
+                text=True,
+                timeout=timeout,
+            )
+        except subprocess.TimeoutExpired as exc:
+            raise LLMTimeoutError(
+                f"claude CLI timed out after {timeout}s",
+                cause=exc,
+            ) from exc
+
+        if result.returncode != 0:
+            raise LLMSubprocessError(
+                f"claude CLI exited with code {result.returncode}",
+                return_code=result.returncode,
+                stderr=result.stderr,
+            )
+
+        content = result.stdout
+        prompt_tokens = estimate_tokens(prompt)
+        completion_tokens = estimate_tokens(content)
+
+        return LLMResponse(
+            content=content,
+            model=self._model or "claude-code-cli",
+            usage={
+                "prompt_tokens": prompt_tokens,
+                "completion_tokens": completion_tokens,
+                "total_tokens": prompt_tokens + completion_tokens,
+            },
+            finish_reason="stop",
+            metadata={
+                "provider": "claude-code",
+                "cli_path": self._cli_path,
+            },
+        )
+
+    def validate_config(self, config: RunConfig) -> bool:
+        try:
+            result = subprocess.run(
+                [self._cli_path, "--version"],
+                capture_output=True,
+                text=True,
+                timeout=10,
+            )
+            return result.returncode == 0
+        except (subprocess.TimeoutExpired, FileNotFoundError, OSError):
+            return False