[Feature Request]: Pre-check GCS path before Bazel build in build_and_sign workflow to avoid redundant CI runs

[Sandesh282]

Is your feature request related to a problem? Please describe.

Currently, the build_and_sign.yml workflow checks whether the signed AAB already exists in GCS after running the full Bazel build. This means that if the same ref is accidentally re-triggered, it wastes the full build time before failing.

Describe the solution you'd like

A better approach would be to check for GCS path existence before the build step. However, this requires knowing the AAB filename up-front, which in turn requires externalizing the version components currently computed inside TransformAndroidManifest (version name, version code, RC number) into a standalone step that can run before the build.

Describe alternatives you've considered

No response

Additional context

Acceptance criteria:

• The GCS path check runs as a dedicated step before bazel build
• TransformAndroidManifest (or a helper) exposes version components so the expected AAB name can be derived without a full build
• The early-exit saves CI time on accidental re-runs of the same ref

[Sandesh282]

@adhiamboperes Can you triage this before I self-assign it?