…tching the backend compiler (#2417)

This change adds `bigframes.pandas.options.experiments.sql_compiler` to
allow switching the backend compiler. Currently, the default remains set
to 'legacy' (ibis), but users can now optionally switch to the
'experimental' (sqlglot) compiler.

Fixes internal issue 479912001🦕

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- [ ] Make sure to open an issue as a
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Fixes #<issue_number_goes_here> 🦕

This should complete the dev on the client side.

Manually verified: https://screenshot.googleplex.com/jv3UfJCm75dCzwn

Related bug 406578908 🦕

This PR refines the visual feedback provided during operation progress.
Specifically, it prevents the display of a standalone "✅ Completed."
message and green checkmark when no query execution information (like
slot time or bytes processed) is available. This often occurs during
metadata-only operations or cached results where the "Completed" status
is redundant.

Fixes #<479944983> 🦕

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

Librarian Version: v0.7.0
Language Image:
us-central1-docker.pkg.dev/cloud-sdk-librarian-prod/images-prod/python-librarian-generator@sha256:e7cc6823efb073a8a26e7cefdd869f12ec228abfbd2a44aa9a7eacc284023677
<details><summary>bigframes: 2.34.0</summary>

##
[2.34.0](v2.33.0...v2.34.0)
(2026-02-02)


### Features

* add `bigframes.pandas.options.experiments.sql_compiler` for switching
the backend compiler (#2417)
([7eba6ee](7eba6ee))
* add bigquery.ml.generate_embedding function (#2422)
([35f3f5e](35f3f5e))
* add bigquery.create_external_table method (#2415)
([76db295](76db295))
* add deprecation warnings for .blob accessor and read_gbq_object_table
(#2408)
([7261a4e](7261a4e))
* add bigquery.ml.generate_text function (#2403)
([5ac6810](5ac6810))


### Bug Fixes

* broken job url (#2411)
([fcb5bc1](fcb5bc1))