Implement LLM-WP-0007: Kimi K3 default and EUR spend reporting

Add moonshotai/kimi-k3 as OpenRouter basemodel default after live smoke,
USD→EUR cost conversion, append-only usage ledger, and CLI run/cost/spend
week commands with token and euro reporting.

llm_connect/adapter.py

@@ -93,6 +93,26 @@ class LLMAdapter(ABC):
         if config.budget_tracker is not None:
             tokens = response.usage.get("total_tokens", 0)
             config.budget_tracker.consume(tokens)
+        self._maybe_record_usage(response)
+
+    def _maybe_record_usage(self, response: LLMResponse) -> None:
+        """Opt-in usage ledger write when ``LLM_CONNECT_USAGE_LEDGER`` is set."""
+        try:
+            from llm_connect.usage import maybe_record_usage
+
+            provider = (
+                (response.metadata or {}).get("provider")
+                or getattr(self, "provider_id", None)
+                or type(self).__name__
+            )
+            maybe_record_usage(
+                response,
+                provider=str(provider),
+                source="library",
+            )
+        except Exception:
+            # Spend accounting must never break inference.
+            return
 
 
 class MockLLMAdapter(LLMAdapter):