chore: clean up unused top-level files

[devin-ai-integration]

Summary

Removes top-level files that are OpenAPI-Generator boilerplate or otherwise unreferenced. Nothing here affects the published lighter-sdk wheel — setup.py already restricts shipped contents to the lighter/ package + py.typed + signers — so this is purely repo cleanup.

Removed:

• git_push.sh — generator-shipped helper, header still references wing328 openapi-petstore-perl; never invoked.
• .travis.yml — Travis CI isn't used; the repo runs on GitHub Actions.
• .gitlab-ci.yml — same; GitLab CI isn't used.
• tox.ini — not referenced by .github/workflows/python.yml or any local script.
• .openapi-generator-ignore — contained only commented-out examples.
• setup.cfg — only held [flake8] max-line-length=99. Stock flake8 doesn't read pyproject.toml without flake8-pyproject, and the GitHub workflow passes --max-line-length=127 on the CLI anyway, so the setting was effectively dead. Dropped instead of inlining.
• test-requirements.txt — dev/test deps are already tracked in pyproject.toml. The GitHub workflow guards this with if [ -f test-requirements.txt ], so removing it doesn't break CI.

Fixed:

• [tool.mypy].files pointed at a non-existent tests/ directory. Switched to test/paper_client, which is where the hand-written tests actually live.

Added:

• publish.sh — the existing release script, committed so it's discoverable. No secrets in it; twine upload reads credentials from ~/.pypirc or TWINE_USERNAME/TWINE_PASSWORD env vars.

Review & Testing Checklist for Human

• Confirm publish.sh is OK to live in a public repo (it has no secrets, but please double-check your release flow doesn't reference any of the deleted files).
• Confirm none of the removed CI configs (.travis.yml, .gitlab-ci.yml, tox.ini) are still being used anywhere external (e.g. a mirror).
• Heads up: .openapi-generator/FILES still lists git_push.sh, setup.cfg, test-requirements.txt, and tox.ini, so next regen will re-create them unless those four lines are pruned from the manifest. (You said you'd handle this manually.)

Notes

Not removed (intentionally), since git history shows they're still in active use for SDK regeneration (commits #129, #126, #109):

• openapi.json, config.yaml, .openapi-generator/FILES, .openapi-generator/VERSION

Other candidates we discussed but left alone:

• docs/ (178 auto-generated .md files) — bulky but useful for GitHub-side reference.
• test/test_account.py — orphan auto-generated stub for Account.
• .github/workflows/python.yml — actually does real work (runs test/paper_client/ across Python 3.8–3.11 on every PR), so keeping. Could be modernized in a follow-up (stale action versions, missing 3.12/3.13, soft flake8 stage).
• The [tool.poetry] block in pyproject.toml is unused since the build uses setuptools/setup.py.

Link to Devin session: https://app.devin.ai/sessions/03760f3186dd461ea5f1ab0e0fa75d92
Requested by: @lavrric

[devin-ai-integration]

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