Create parent directories for local memory persistence

[onyx679]

Summary

This updates LocalConversationMemoryDriver.store() to create the parent directory for persist_file before writing persisted conversation memory.

Previously, using a nested path such as memory/test_memory.json raised FileNotFoundError if the parent directory did not already exist.

Changes

• Create persist_file.parent with parents=True, exist_ok=True before writing.
• Add a unit test covering nested local conversation memory persistence paths.

Tests

• D:\简历\griptape\.venv\Scripts\python.exe -m pytest tests/unit/drivers/memory/conversation/test_local_conversation_memory_driver.py -q
• D:\简历\griptape\.venv\Scripts\python.exe -m pytest tests/unit/drivers/memory/conversation -q
• D:\简历\griptape\.venv\Scripts\python.exe -m ruff check griptape/drivers/memory/conversation/local_conversation_memory_driver.py tests/unit/drivers/memory/conversation/test_local_conversation_memory_driver.py
• git diff --check

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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