Pinscope open-source core

Agentic schematic validation: datasheet extraction via Claude Console
Skills, netlist/BOM design graph, per-IC direct datasheet review with
page citations, capacitor derating, Next.js report UI.

Extracted from the Pinscope cloud codebase. Auth and billing live in the
private gateway repo behind stable seams (billing_hook.py, adapter files
listed in CLAUDE.md).

backend/services/llm/__init__.py

@@ -0,0 +1,36 @@
+"""Provider-agnostic LLM client layer.
+
+All Claude API calls in the backend route through this package via the
+``LLMProvider`` interface. The default provider is Anthropic; per-stage
+overrides via ``Settings.provider_*`` env vars route specific stages to
+other providers (currently Anthropic + Gemini).
+"""
+
+from backend.services.llm.factory import call_with_fallback, get_provider
+from backend.services.llm.types import (
+    Completion,
+    ContentBlock,
+    Message,
+    PdfBlock,
+    TextBlock,
+    ToolCall,
+    ToolChoice,
+    ToolResultBlock,
+    ToolSchema,
+    Usage,
+)
+
+__all__ = [
+    "Completion",
+    "ContentBlock",
+    "Message",
+    "PdfBlock",
+    "TextBlock",
+    "ToolCall",
+    "ToolChoice",
+    "ToolResultBlock",
+    "ToolSchema",
+    "Usage",
+    "call_with_fallback",
+    "get_provider",
+]