When using multiplexed sessions, the transaction_tag should also be set
on the BeginTransactionRequest.

---------

Co-authored-by: rahul2393 <irahul@google.com>

…1472)

1. add cryptography to prerelease dependencies
The prerelease dependency check installs packages with `--no-deps`,
which causes `google-auth` to fail because its dependency `cryptography`
and `cffi` is missing. This change explicitly adds `cryptography` and
`cffi` to the `prerel_deps` list in `noxfile.py` to ensure it is
installed during the test session.

2. bypass sqlparse for RUN PARTITION commands
Check for RUN PARTITION command to avoid sqlparse processing it.
sqlparse fails with "Maximum grouping depth exceeded" on long partition
IDs causing flakiness in system tests.

Signed-off-by: Sri Harsha CH <sriharshach@google.com>
Co-authored-by: Subham Sinha <suvham@google.com>

***Handle errors during stream restart in snapshot***

**Root Cause**
When `_restart_on_unavailable` caught a `ServiceUnavailable` or
resumable `InternalServerError`, it attempted to re-initialize the
iterator immediately within the `except` block. If this
re-initialization failed (e.g. due to a persistent transient error), the
exception would propagate unhandled, breaking the retry loop.

**Fix**
This change modifies the logic to reset the iterator to `None` and
`continue` the loop, forcing the re-initialization to occur inside the
`try` block. This ensures that subsequent errors during restart are
properly caught and retried.

**Testing**
Added unit tests to cover this specific behavior

PR created by the Librarian CLI to initialize a release. Merging this PR
will auto trigger a release.

Librarian Version: v1.0.0
Language Image:
us-central1-docker.pkg.dev/cloud-sdk-librarian-prod/images-prod/python-librarian-generator@sha256:b8058df4c45e9a6e07f6b4d65b458d0d059241dd34c814f151c8bf6b89211209
<details><summary>google-cloud-spanner: 3.62.0</summary>

##
[3.62.0](v3.61.0...v3.62.0)
(2026-01-14)

### Features

* add uuid support (#1310)
([3b1792a](3b1792aa))

### Bug Fixes

* transaction_tag should be set on BeginTransactionRequest (#1463)
([3d3cea0](3d3cea0b))

* resolve pre-release dependency failures and sqlparse recursion (#1472)
([9ec95b7](9ec95b7d))

* handle errors during stream restart in snapshot (#1471)
([c066873](c0668735))

</details>