chore(librarian): onboard to librarian (#796)

Towards googleapis/librarian#2460

---------

Co-authored-by: Knut Olav Løite <koloite@gmail.com>
Co-authored-by: ohmayr <omairn@google.com>

Author: 3 people

.github/release-please.yml

@@ -0,0 +1,10 @@
+image: us-central1-docker.pkg.dev/cloud-sdk-librarian-prod/images-prod/python-librarian-generator@sha256:c8612d3fffb3f6a32353b2d1abd16b61e87811866f7ec9d65b59b02eb452a620
+libraries:
+  - id: sqlalchemy-spanner
+    version: 1.17.1
+    apis: []
+    source_roots:
+      - .
+    preserve_regex: []
+    remove_regex: []
+    tag_format: v{version}

.github/release-trigger.yml

@@ -1,5 +1,9 @@
 # Changelog
 
+[PyPI History][1]
+
+[1]: https://pypi.org/project/sqlalchemy-spanner/#history
+
 ## [1.17.1](https://github.com/googleapis/python-spanner-sqlalchemy/compare/v1.17.0...v1.17.1) (2025-10-21)