[v1.x] fix: return HTTP 404 for unknown session IDs instead of 400#1945

maxisbey merged 1 commit intomodelcontextprotocol:v1.xmodelcontextprotocol/python-sdk:v1.xfrom

LucaButBoring:fix/1808-backport-v1.xLucaButBoring/mcp-python-sdk:fix/1808-backport-v1.xCopy head branch name to clipboard