feat: add Claude backend with automatic Ollama fallback (Claudification Phase 1)

All agents now prefer Claude API when ANTHROPIC_API_KEY is configured,
with automatic fallback to Ollama when offline or unconfigured. New
src/anthropic/ module provides model selection via get_model() factory.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/anthropic/__init__.py

@@ -0,0 +1,17 @@
+"""
+Anthropic/Claude integration module.
+
+Provides model selection with automatic fallback between Claude and Ollama.
+"""
+
+from src.anthropic.model_selector import (
+    check_claude_health,
+    get_model,
+    is_claude_available,
+)
+
+__all__ = [
+    "check_claude_health",
+    "get_model",
+    "is_claude_available",
+]