🧪 test: add comprehensive tests for usePending React hook

[johnstrand]

🎯 What: The usePending React hook in src/Squawk.ts was entirely untested. This PR adds a comprehensive test suite for it using react-test-renderer.

📊 Coverage: The new tests cover:

• Tracking pending state correctly for implicitly accessed contexts using proxy tracking.
• Tracking pending state correctly for explicitly specified contexts.
• State updates flowing through from store.action() execution correctly.

✨ Result: Improved test coverage and robust safety net to confidently refactor usePending in the future.

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PR created automatically by Jules for task 13960321370991834614 started by @johnstrand

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