feat(checkpoint)!: sort list/alist by checkpoint ID descending (#106)

[bsbodden]

Add sort_by parameter to FilterQuery in all list/alist implementations
to return checkpoints in descending order (newest first). This matches
SQLite checkpointer behavior and enables efficient lookup of recent/
crashed sessions without fetching all checkpoints into memory.

Updated implementations:

• AsyncRedisSaver.alist() (aio.py:709)
• RedisSaver.list() (init.py:279)
• AsyncShallowRedisSaver.alist() (ashallow.py:384)
• ShallowRedisSaver.list() (shallow.py:334)

BREAKING CHANGE: Checkpoints are now returned in DESC order (newest
first) instead of ASC order (oldest first). Code that accessed the
most recent checkpoint with list(saver.list(config))[-1] must now
use list(saver.list(config))[0].

Fixes #106

[Copilot]

Pull Request Overview

This PR implements descending sort order for checkpoint listings by checkpoint ID, ensuring the newest checkpoints appear first in all Redis checkpoint implementations. This change aligns with SQLite checkpointer behavior and enables efficient retrieval of recent or crashed sessions without loading all checkpoints into memory.

Key Changes:

• Added sort_by=("checkpoint_id", "DESC") parameter to FilterQuery in list/alist methods
• Updated test assertions to access the first element (newest) instead of the last element (oldest)
• Added comprehensive test coverage for sort order behavior across multiple scenarios

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
langgraph/checkpoint/redis/init.py	Added DESC sort parameter to RedisSaver.list() FilterQuery
langgraph/checkpoint/redis/aio.py	Added DESC sort parameter to AsyncRedisSaver.alist() FilterQuery
langgraph/checkpoint/redis/shallow.py	Added DESC sort parameter to ShallowRedisSaver.list() FilterQuery
langgraph/checkpoint/redis/ashallow.py	Added DESC sort parameter to AsyncShallowRedisSaver.alist() FilterQuery
tests/test_streaming.py	Updated test assertions to access newest checkpoint at index [0] instead of [-1]
tests/test_alist_sort_order.py	Added new comprehensive test suite validating DESC sort order for both sync and async implementations

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[Copilot]

Pull Request Overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated no new comments.

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