Add generated SDK import smoke test

[ivanleomk]

Summary

Adds a lightweight unittest smoke test for generated SDK import integrity.

The test verifies that:

• import kagglesdk succeeds
• every discovered kagglesdk.* module imports cleanly
• KaggleClient() instantiates
• the expected top-level client groups are present
• the generated client exposes 21 nested *_client subclients

Why

The 0.1.31/0.1.32 import regression was caused by generated files referencing modules that were not included in the synced/published package. A build-only release step can still succeed in that case because wheel construction does not import the full transitive module graph.

This gives the release flow a cheap import-closure check that catches missing generated modules before publishing.

Evidence

Current main plus this test fails after installing the project into a fresh environment:

ModuleNotFoundError: No module named 'kagglesdk.competitions.legacy'

Ran 2 tests in 1.218s
FAILED (errors=2)

The same test overlaid onto origin/fix-imports-0.1.33 passes:

Ran 2 tests in 1.852s
OK

Reproduction commands

Run the test on this branch, which is based on current main and demonstrates the missing-import failure:

git fetch origin
git checkout import-smoke-test
uv run --with-editable . python -m unittest tests.test_import_smoke

Run the exact same test against the 0.1.33 fix branch by saving this PR's test file before switching branches:

cp tests/test_import_smoke.py /tmp/test_import_smoke.py
git checkout origin/fix-imports-0.1.33
mkdir -p tests
cp /tmp/test_import_smoke.py tests/test_import_smoke.py
uv run --with-editable . python -m unittest tests.test_import_smoke
rm /tmp/test_import_smoke.py

[stevemessick]

This looks like a good idea. We will need to add it to the code generator and link in some GitHub checks.