🧪 [testing improvement] Add tests for Memory.unwatch

[dioncx]

🎯 What: The testing gap for Memory.unwatch in json_memory/memory.py:108 has been addressed. The method was previously untested.

📊 Coverage: Added tests to verify:

• Unwatching specific callbacks.
• Unwatching all callbacks for a specific path.
• Handling non-existent paths gracefully.

✨ Result: Memory.unwatch is now thoroughly tested, increasing code reliability, and ensuring confident refactoring. All 335 tests pass smoothly.

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PR created automatically by Jules for task 14717262610975677260 started by @dioncx

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