chore(integrations): remove defunct langgraph-python-threads example (ENT-800) (CopilotKit#5281)

## Summary

Removes `examples/integrations/langgraph-python-threads/` (87 files) and
its two entries in `.github/config-allowlist.txt`.

The standalone "LangGraph Python + durable threads" template is defunct:

- The ENT-679 threads rollout was fully reverted from main on 2026-06-04
(CopilotKit#5215/CopilotKit#5216/CopilotKit#5217); the settled model is base `langgraph-python` +
Intelligence activation overlay, not a duplicate `-threads` template.
- The Intelligence CLI no longer scaffolds from it — verified zero
references on Intelligence `main` (a806a7e0) **and** in the published
`copilotkit@3.0.2` npm tarball.

## Verification

- `git grep langgraph-python-threads` across the tracked tree returns
nothing after this change (no hits in `pnpm-workspace.yaml`,
`pnpm-lock.yaml`, `_parity` manifest, CI workflows, or READMEs).
- The example was standalone (npm-based, not a pnpm workspace member,
not an Nx project) — zero workspace projects structurally affected.
- Lefthook commit gates green: check-binaries, sync-lockfile, lint-fix,
`nx run-many -t test --projects=packages/**` (25/25).
- `nx run-many -t lint,build --projects=packages/**`: all green except
pre-existing `@copilotkit/vue:lint` failures on main (files untouched by
this diff, introduced in 913c36b).

Linear: ENT-800

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Author: BenTaylorDev

.github/config-allowlist.txt

@@ -17,8 +17,6 @@ examples/integrations/crewai-crews/next.config.ts
 examples/integrations/crewai-flows/next.config.ts
 examples/integrations/langgraph-fastapi/next.config.ts
 examples/integrations/langgraph-js/next.config.ts
-examples/integrations/langgraph-python-threads/apps/app/src/vite-env.d.ts
-examples/integrations/langgraph-python-threads/apps/app/vite.config.ts
 examples/integrations/langgraph-python/next.config.ts
 examples/integrations/llamaindex/next.config.ts
 examples/integrations/mastra/next.config.ts