[dchebrolu]

What

• Add CI on PRs, pushes to master, weekly schedules, and manual execution.
• Automatically discover and test every stable Python release line from 3.11 through the latest release.
• Replace obsolete Tox targets and Nose with modern Python targets and unittest.
• Use unittest.mock instead of the standalone mock package.
• Add isolated package builds and smoke checks for both wheel and source distributions.
• Add concise local verification instructions.

Why

INTST-1757 requires scheduled compatibility checks to catch runtime issues without waiting for library changes.

The existing test configuration targeted obsolete Python versions. The updated pipeline runs the suite on modern runtimes and verifies that both distribution formats can be installed, imported, and used for a basic request.

Verification

• Local act and GitHub PR CI passed on Python 3.11–3.15: 5 runtime jobs.
• All 9 unit tests passed per runtime.
• Wheel and source-distribution installation, import, and local API-request smoke tests passed.
• All 3 runtime-discovery tests passed.

Pending after merge

• Verify the push-to-master run.
• Verify manual execution.
• Confirm an actual weekly scheduled run.

[Copilot]

🟢 Approval recommended

No blocking issues were identified in the CI configuration, packaging flow, or isolated smoke checks.

No open issues 🎉

What changed in this PR

Adds scheduled compatibility checks and isolated package smoke tests for the Python client.

Changes:

• Runs CI on pull requests, master pushes, weekly schedules, and manual triggers.
• Builds and validates wheel and source distributions using local requests.
• Modernizes test tooling and documents tested Python versions.

File	Description
tox.ini	Runs unit tests and package smoke checks.
test/​test_sailthru_client.py	Uses standard-library mocks.
test/​smoke-package.py	Tests the installed client against a loopback server.
scripts/​test-package.py	Builds and validates both distributions in isolated environments.
README.md	Documents compatibility targets and test commands.
pyproject.toml	Declares the package build backend.
.github/​workflows/​code-check.yml	Adds scheduled and event-driven Python compatibility checks.

_{Review effort: Balanced}