fix(mcp): capture scraper logs and return them in tool responses

Scraper debug output goes to stderr which is invisible in MCP stdio mode.
Add capture_logs context manager that attaches a StringIO handler to the
schwab_scraper logger during tool execution, then includes captured logs
in the response envelope when debug=True or on failure.

Applied to login() and refresh_session() which are the critical paths
for authentication diagnostics.

server.py

@@ -1,7 +1,9 @@
+import io
 import json
 import logging
 import os
 import time
+from contextlib import contextmanager
 from typing import Optional, Any, Tuple
 
 from fastmcp import FastMCP
@@ -12,6 +14,45 @@ import uvicorn
 
 import schwab_scraper.unified_api as api
 
+
+# ---------------------------------------------------------------------------
+# Log capture helper — scraper logs go to stderr which is invisible in MCP
+# stdio mode.  This captures them so we can return them in the response.
+# ---------------------------------------------------------------------------
+@contextmanager
+def capture_logs(logger_name: str = "schwab_scraper", level: int = logging.DEBUG):
+    """Context manager that captures log output to a string buffer.
+
+    Yields the buffer so callers can read captured logs after the block.
+    """
+    logger = logging.getLogger(logger_name)
+    # Ensure the logger will actually process messages at this level
+    old_level = logger.level
+    if old_level > level:
+        logger.setLevel(level)
+
+    buf = io.StringIO()
+    handler = logging.StreamHandler(buf)
+    handler.setLevel(level)
+    # Match the format used by the scraper
+    handler.setFormatter(logging.Formatter("%(asctime)s - %(name)s - %(levelname)s - %(message)s"))
+    logger.addHandler(handler)
+
+    try:
+        yield buf
+    finally:
+        logger.removeHandler(handler)
+        logger.setLevel(old_level)
+
+
+def _enrich_with_logs(result: dict, log_buffer: io.StringIO, debug: bool) -> dict:
+    """Attach captured logs to a result dict when debug=True or on error."""
+    logs = log_buffer.getvalue()
+    if logs and (debug or not result.get("success", False)):
+        result["logs"] = logs
+    return result
+
+
 # ---------------------------------------------------------------------------
 # Monkey-patch mcp.shared.session.RequestResponder to work around a
 # cancellation race in mcp==1.27.0 (github.com/modelcontextprotocol/
@@ -177,9 +218,11 @@ async def login(
             "data": None,
         })
 
+    with capture_logs(level=logging.DEBUG if debug else logging.INFO) as log_buf:
         result = await api.login(username=username, password=password, debug=debug)
         success = result.get("success", False)
         login_manager.record_attempt(success)
+        result = _enrich_with_logs(result, log_buf, debug)
     return serialize(result)
 
 
@@ -190,7 +233,9 @@ async def refresh_session(debug: bool = False) -> str:
     Args:
         debug: Enable debug logging
     """
+    with capture_logs(level=logging.DEBUG if debug else logging.INFO) as log_buf:
         result = await api.refresh_session(debug=debug)
+        result = _enrich_with_logs(result, log_buf, debug)
     return serialize(result)