refactor(sdk): enable ruff isort and sort imports tree-wide

[quanghexa94]

Enable ruff's import-sorting (isort, rule I) for the Hexgate SDK and sort every import block in the tree so the ordering is enforced going forward. Pure chore, SDK only (hexgate + tests): no runtime behaviour changes, no new dependency, no platform change. This is a standalone PR off main and does not depend on any in-flight agent-enforcement work.

Design

extend-select = ["I"] is added under a new [tool.ruff.lint] in the root pyproject.toml. extend-select (not select) is deliberate: the repo had no [tool.ruff] section, so ruff was running its default rule set (E4/E7/E9, F). Using select would have silently dropped those defaults; extend-select layers isort on top and keeps them. The rest of the diff is entirely ruff check --fix output, reordering existing import statements. No imports were added or removed, only sorted and grouped (stdlib / third-party / first-party).

Important files

File	What to look at
pyproject.toml	the new [tool.ruff.lint] with extend-select = ["I"]; confirm it does not clobber the default E/F rules
hexgate/**, tests/**	mechanical import reorders only; no logic changes

Test plan

Ran from the SDK worktree with the project's env:

• ruff check hexgate tests after the fix: All checks passed! (before the fix it reported 63 errors, all rule I, all auto-fixed).
• ruff format --check hexgate tests: 274 files already formatted (the reorders did not disturb formatting).
• Full unit suite python -m pytest tests/ -q: 2075 passed, 6 skipped, 20 deselected in ~19s, zero errors. This is the check that matters for an import reorder, a bad reorder would surface as an ImportError at collection time (for example a circular import in an __init__.py). Collection was clean and no module needed a # noqa: I001 guard.

A reviewer can catch a regression by re-running the three commands above; ruff check now fails CI on any unsorted import.

Try it

ruff check hexgate tests
ruff format --check hexgate tests
python -m pytest tests/ -q

Notes

• Scope is the SDK only. platform/api is a separate uv project with its own pyproject.toml and ruff config; enabling isort there is a sensible follow-up in a separate PR and is intentionally left out here.
• No behaviour change and nothing to roll back beyond reverting the commit.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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