fix: partition shard items with comprehensions for the SonarCloud gate

[Brad-Edwards]

Summary

dev fails the required sonar check at 2a5b0f46. The SonarCloud quality gate has one new violation (new_violations = 1): python:S9409 in tools/pytest_shard_plugin.py:71, an append() inside a for-loop. The same gate blocks the dev → main PR #1402. This PR partitions shard items with comprehensions, which fixes the finding without changing behavior.

Requirement UIDs

• None. This is a code-quality fix to test tooling with no requirement scope.

Related Issues

No issue: remediates the SonarCloud gate failure on dev.

ADR Impact

• None.

Changes

• tools/pytest_shard_plugin.py: each item's shard assignment is computed once, then split into owned and deselected lists with comprehensions instead of a loop that appends to one list or the other. Ordering and the deselection hook are unchanged.

Test Plan

• Unit tests pass
• Integration tests pass if applicable
• Full completion suite required in CI before merge
• No coverage regression

tests/test_pytest_shard.py and tests/test_nox_shard_wiring.py pass (46). nox -s verify-fast-feedback --base-rev origin/dev and tools/check_tooling_artifact_policy.py pass.

Ground Control Checks

• SonarCloud finding addressed in code, not suppressed

Traceability

• SonarCloud dev quality gate: new_violations 1 (python:S9409, tools/pytest_shard_plugin.py:71); CI run 36804584166, job sonar

Checklist

• No security or quality gate weakened
• Behavior-preserving change verified by the shard tests