fix: expose Polymarket auth initialization in SDKs

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Fixes #505

Changes

• add Polymarket.initAuth() to the TypeScript SDK
• generate Polymarket.init_auth() for the Python SDK so it survives the exchange wrapper generator
• add a small regression test that checks the Python wrapper keeps forwarding to the core initAuth method

Verification

• node core/scripts/generate-python-exchanges.js
• python -m pytest sdks/python/tests/test_public_exports.py
• TypeScript syntax check via typescript.transpileModule on sdks/typescript/pmxt/client.ts
• git diff --check

I couldn't run the full TypeScript package build in this Windows checkout: the clean script uses rm -rf, and generating the missing OpenAPI client locally needs Java, which isn't installed here.