fix(checkpoint): ensure write_keys_zset uses storage-safe sentinel va…

[bsbodden]

…lues

The make_write_keys_zset_key method was not converting empty checkpoint_ns values to the "empty" sentinel, causing a mismatch between keys created during put_writes and keys searched during delete_thread.

This resulted in write_keys_zset sorted sets not being cleaned up when delete_thread was called, leaving orphaned keys in Redis.

Changes:

• Update make_write_keys_zset_key to use to_storage_safe_id and to_storage_safe_str for consistent key generation
• Fix key registry initialization to properly initialize after Redis client configuration in setup() method
• Add comprehensive integration tests covering sync/async deletion scenarios with empty and non-empty checkpoint namespaces

Fixes #104

[Copilot]

Pull Request Overview

This PR fixes a bug where the write_keys_zset sorted sets were not being properly cleaned up during thread deletion due to inconsistent key generation between the put_writes and delete_thread operations, specifically when handling empty checkpoint namespace values.

• Updates the make_write_keys_zset_key method to use storage-safe conversion functions for consistent key generation
• Fixes initialization order of the key registry to ensure proper Redis client configuration
• Adds comprehensive integration tests covering sync/async deletion scenarios with various checkpoint namespace configurations

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
tests/test_issue_104_delete_write_keys_zset.py	New comprehensive test suite verifying write_keys_zset cleanup during thread deletion
langgraph/checkpoint/redis/key_registry.py	Updated make_write_keys_zset_key method to use storage-safe conversion functions
langgraph/checkpoint/redis/init.py	Fixed key registry initialization order in RedisSaver constructor

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