[codex] build Docker SSI images with Rebuildr

[pawelchcki]

Summary

• replace manual Docker SSI image handling with separate cached and per-run Rebuildr DAGs
• pin reusable image identity to the base registry digest and tracked build inputs
• enforce CI/local publication policy and update CLI/wizard behavior
• capture Buildx Bake output and add focused DAG, cache, and publication tests

Why

The previous flow used mutable tags, manual existence checks, Docker SDK builds, and teardown publication. That made cache invalidation implicit and allowed stale reusable images. Rebuildr provides content-addressed cache identities while keeping tracer and injector installation intentionally movable.

Impact

GitLab CI always publishes cache-aware reusable images and now fails early without PRIVATE_DOCKER_REGISTRY. Local runs only read or build by default; -P explicitly opts into publication. The removed -B option is no longer needed because tracked inputs invalidate the cached graph automatically.

Validation

• ./format.sh
• venv/bin/pytest -q --scenario TEST_THE_TEST tests/test_the_test/test_docker_ssi_image_builder.py (12 passed)
• cold and warm Python 3.12.7 / Ubuntu 22.04 AMD64 DOCKER_SSI smoke runs (3 passed each, with expected skip/xfail/xpass outcomes)
• warm run confirmed the reusable DAG was skipped while SSI/weblog rebuilt with a fresh nonce

[datadog-datadog-us1-prod]

✨ Fix all issues with BitsAI

⚠️ Warnings

🚦 7 Pipeline jobs failed

DataDog/system-tests | mirror_images     

DataDog/system-tests | compute_pipeline     

DataDog/system-tests | system_tests_param     

View all 7 failed jobs.

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[github-actions]

CODEOWNERS have been resolved as:

tests/test_the_test/test_docker_ssi_image_builder.py                    @DataDog/system-tests-core
utils/docker_ssi/image_builder.py                                       @DataDog/system-tests-core
utils/docker_ssi/ssi-installer.rebuildr.py                              @DataDog/system-tests-core
utils/docker_ssi/weblog-injection.rebuildr.py                           @DataDog/system-tests-core
conftest.py                                                             @DataDog/system-tests-core
pyproject.toml                                                          @DataDog/system-tests-core
requirements.txt                                                        @DataDog/system-tests-core
utils/_context/_scenarios/docker_ssi.py                                 @DataDog/system-tests-core
utils/build/ssi/base/base_ssi.Dockerfile                                @DataDog/system-tests-core
utils/build/ssi/base/base_ssi_installer.Dockerfile                      @DataDog/system-tests-core
utils/build/ssi/base/install_script_ssi_installer.sh                    @DataDog/system-tests-core
utils/scripts/ssi_wizards/docker_ssi_wizard.sh                          @DataDog/system-tests-core