fix(serve): catch BrokenPipeError/ConnectionResetError in _json_response

Fixes #64: serve.py crashed with BrokenPipeError when an HTTP client
disconnected before the server finished writing the response. The
_json_response() method wrote to self.wfile with no exception handling.

Changes:
- Wrap entire response-writing block in try/except
- Catch (BrokenPipeError, ConnectionResetError) silently
- Client disconnects no longer produce noisy tracebacks

Author: wycfirezdog

src/tracer/runtime/serve.py

@@ -94,12 +94,15 @@ def _read_body(self) -> dict:
 
     def _json_response(self, code: int, data: dict):
         body = json.dumps(data, default=str).encode("utf-8")
-        self.send_response(code)
-        self.send_header("Content-Type", "application/json")
-        self.send_header("Content-Length", str(len(body)))
-        self.send_header("Access-Control-Allow-Origin", "*")
-        self.end_headers()
-        self.wfile.write(body)
+        try:
+            self.send_response(code)
+            self.send_header("Content-Type", "application/json")
+            self.send_header("Content-Length", str(len(body)))
+            self.send_header("Access-Control-Allow-Origin", "*")
+            self.end_headers()
+            self.wfile.write(body)
+        except (BrokenPipeError, ConnectionResetError):
+            pass  # client disconnected
 
     def log_message(self, fmt, *args):
         # Quiet logging - only errors