[codex] Add Firebase release updater tooling

[AdamEssenmacher]

Summary

• Add Cake release tooling for Firebase line bumps with read-only firebase-release-check and mutating firebase-release-update targets.
• Cover deterministic release metadata: component artifact versions, Firebase-family PodSpec pins, external download metadata, project/package versions, targets metadata, Crashlytics script URL, audit/E2E package versions, native framework metadata, and linker flags.
• Add dependency-first Firebase packing behavior and repo-local output/ restore source support for package validation.
• Normalize current 12.6 audit/E2E validation metadata so the new checker is clean on main without carrying generated 12.7 release changes.

Not Included

• No generated 12.7 package/version bump files.
• No docs, samples, README, binding definition, output, or GitHub automation changes.

Validation

• dotnet tool restore
• dotnet tool run dotnet-cake -- --target=firebase-release-check --firebase-version=12.6.0
• dotnet test scripts/FirebaseBindingAudit.Tests/FirebaseBindingAudit.Tests.csproj

[chatgpt-codex-connector]

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