fix: tool registry emits Anthropic schema, question lifecycle cleanup

- Tool.to_schema() emits input_schema (Anthropic Messages API) instead
  of OpenAI-style parameters
- QuestionManager: remove questions from _pending on answer and timeout,
  reject double answers, add list_pending()
- core/skills/__init__.py so skills are importable as a package
- revert optional-import fallbacks in logger/message_bus: nats-py and
  loguru are hard requirements, a broken install should fail loudly
- tests for wait_for_answer happy path and timeout cleanup

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012AJLYcbTHCe45fyFnMfEin

core/logger.py

@@ -1,33 +1,27 @@
-"""Structured logging for LogiFlow AI — loguru setup with standard logging fallback."""
+"""Structured logging for LogiFlow AI — single loguru setup imported by all modules."""
 import sys
 import os
-import logging
 from pathlib import Path
+from loguru import logger
 
-try:
-    from loguru import logger
+Path("logs").mkdir(exist_ok=True)
 
-    Path("logs").mkdir(exist_ok=True)
+logger.remove()
 
-    logger.remove()
+logger.add(
+    sys.stderr,
+    format="{time:YYYY-MM-DD HH:mm:ss} | {level: <8} | {name}:{function}:{line} - {message}",
+    level=os.getenv("LOG_LEVEL", "INFO"),
+    colorize=False,
+)
 
-    logger.add(
-        sys.stderr,
-        format="{time:YYYY-MM-DD HH:mm:ss} | {level: <8} | {name}:{function}:{line} - {message}",
-        level=os.getenv("LOG_LEVEL", "INFO"),
-        colorize=False,
-    )
-
-    logger.add(
-        "logs/logiflow_{time:YYYY-MM-DD}.log",
-        rotation="100 MB",
-        retention="30 days",
-        compression="gz",
-        level="DEBUG",
-        format="{time:YYYY-MM-DD HH:mm:ss} | {level: <8} | {name}:{function}:{line} - {message}",
-    )
-except ImportError:
-    logging.basicConfig(level=logging.INFO, format="%(asctime)s | %(levelname)-8s | %(message)s")
-    logger = logging.getLogger("logiflow")
+logger.add(
+    "logs/logiflow_{time:YYYY-MM-DD}.log",
+    rotation="100 MB",
+    retention="30 days",
+    compression="gz",
+    level="DEBUG",
+    format="{time:YYYY-MM-DD HH:mm:ss} | {level: <8} | {name}:{function}:{line} - {message}",
+)
 
 __all__ = ["logger"]