Picks up _extract_forwarded_headers_from_config from PR #4984, now
shipped as copilotkit 0.1.91 on PyPI. Three Python integrations move
forward together: langgraph-python, strands, langgraph-fastapi.
Updates validate-pins ratchet hash (count stays 106, FAIL set shifted
because showcase pins now diverge from Dojo on 0.1.91 vs 0.1.87).
Showcase auto-redeploys to Railway on merge via showcase_build.yml
(path filter showcase/**).
Pin copilotkit==0.1.90 across the three CopilotKit-aware Python
integrations (langgraph-python, strands, langgraph-fastapi) so the
forwarded-header extraction from this PR is the version that runs in
showcase. Bump ag-ui-langgraph to >=0.0.35 with the [fastapi] extra in
langgraph-fastapi because copilotkit 0.1.90 requires it transitively;
the previous ==0.0.34 pin would cause pip install to hard-fail.
The showcase framework directories better reflect their role as
integration examples rather than distributable packages.
Renames showcase/packages/ -> showcase/integrations/ and updates
the test docker-compose file reference accordingly.
Jordan Ritter