Polish SDK packaging metadata

[GsCommand]

Motivation

• Close small packaging and release-surface gaps so clean installs and PyPI metadata render correctly.
• Ensure TypeScript explicitly declares Node types to avoid accidental transitive dependencies.
• Provide canonical repo/documentation/changelog links for the Python package to improve PyPI optics.

Description

• Add @types/node under devDependencies in typescript-sdk/package.json to declare Node typings explicitly.
• Replace the python-sdk/pyproject.toml [project.urls] block with concrete Homepage, Repository, Documentation, and Changelog URLs pointing at the repo.
• Add a root CHANGELOG.md with a concise 1.1.0 entry documenting the canonical receipt model and packaging/typing changes.
• Link CHANGELOG.md from the top-level README.md so the changelog is discoverable from the main docs.

Testing

• Attempted a clean TypeScript validation with rm -rf node_modules package-lock.json && npm install && npm run typecheck && npm run build && npm test, but npm install failed with a 403 Forbidden when fetching @types/node, preventing typecheck, build, and test from completing.
• Running tsc after the failed install produced missing Node type errors because local dev dependencies were unavailable.
• Attempted python -m build and twine check dist/*, but the environment lacked the build tool and pip installs of build/twine were blocked by a proxy 403, so packaging checks could not run.
• Automated local inspections confirmed the pyproject.toml URL block is present and that CHANGELOG.md is created and linked from README.md (non-network file checks succeeded).

---

Codex Task