ci(conformance): pin harness to 0.2.0-alpha.3 with expected-failures baseline by maxisbey · Pull Request #2877 · modelcontextprotocol/python-sdk

…baseline

Modernizes the conformance CI to match the typescript-sdk pattern:

- Pin @modelcontextprotocol/conformance via a single workflow-level
  CONFORMANCE_VERSION env var (was 0.1.10/0.1.13, drifted between jobs).
- Add .github/actions/conformance/expected-failures.yml so the runner
  exits 0 on known-failing scenarios and 1 on regressions or stale
  entries. Client baseline is 16 scenarios grouped by SEP; server
  active suite is fully green.
- Drop continue-on-error from both jobs so conformance actually gates.
- Harden run-server.sh with a port-conflict guard, dead-process check,
  and curl --max-time, mirroring typescript-sdk's wrapper.

The server --suite draft step (2026-07-28 scenarios) is a follow-up;
the baseline file already has a placeholder for it.

Supersedes #1921.