CI: Python and TypeScript workflows run twice per PR commit (push + pull_request) #5048

Problem

.github/workflows/python.yml and .github/workflows/typescript.yml trigger on both push and pull_request. Every commit pushed to a branch with an open PR therefore runs each workflow twice, and the PR's checks list shows every job twice: once (push), once (pull_request).

Expected

One CI run per commit.

Fix

Do what the Inspector does (modelcontextprotocol/inspector#1297): trigger on push only. Fork PRs, the one case push alone misses, are no longer accepted here.