Deterministic Commit Message Builder for Dependency Updater

[dxbr]

Description

This update addresses an issue in the dependency updater where commit titles and descriptions were generated in a nondeterministic order due to iterating over a Go map.
The changes ensure that dependency updates are alphabetically sorted before composing commit metadata, resulting in stable, predictable commit messages.
Unit tests have been added to verify deterministic formatting and to ensure the original dependency slice is not mutated.

Summary

• Ensure the dependency updater builds commit titles and descriptions from a stable, alphabetically sorted dependency list.
• Add unit tests that exercise deterministic formatting behavior and guard against slice mutation.

Testing

• ✅ go test ./...

Notes

These improvements guarantee consistent commit messages across runs, improving traceability, CI reliability, and reducing random diffs in automated dependency updates.

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1