fix: monkey-patch mcp cancellation race crash (SDK issue #2416)

Patch RequestResponder.respond() and cancel() at startup to handle
the race where a notifications/cancelled arrives between handler
return and respond(), which crashes the session with
"AssertionError: Request already responded to".

Also improve build.sh to handle registry push failures gracefully
and auto-restart the container after building.

server.py

@@ -1,4 +1,5 @@
 import json
+import logging
 import os
 from typing import Optional, Any
 
@@ -11,6 +12,40 @@ import uvicorn
 # Import the unified API from the schwab_scraper dependency
 import schwab_scraper.unified_api as api
 
+# ---------------------------------------------------------------------------
+# Monkey-patch mcp.shared.session.RequestResponder to work around a
+# cancellation race in mcp==1.27.0 (github.com/modelcontextprotocol/
+# python-sdk/issues/2416).  A concurrent notifications/cancelled can set
+# _completed=True between handler return and respond(), crashing the session
+# with "AssertionError: Request already responded to".
+# Remove once upstream ships a fix (likely mcp>=1.28).
+# ---------------------------------------------------------------------------
+def _patch_request_responder():
+    from mcp.shared.session import RequestResponder
+
+    _orig_respond = RequestResponder.respond
+
+    async def _safe_respond(self, response):
+        if self._completed:
+            logging.debug(
+                "respond() skipped for request %s — already completed (race with cancel)",
+                self.request_id,
+            )
+            return
+        return await _orig_respond(self, response)
+
+    _orig_cancel = RequestResponder.cancel
+
+    async def _safe_cancel(self):
+        if self._completed:
+            return
+        return await _orig_cancel(self)
+
+    RequestResponder.respond = _safe_respond
+    RequestResponder.cancel = _safe_cancel
+
+_patch_request_responder()
+
 # Initialize FastMCP
 mcp = FastMCP("SchwabScraper")