fix: replace raw echo with output helpers in git/all-to-default-branch

[github-actions]

Summary

• Replace all raw echo calls in git/all-to-default-branch with the standard output helpers (info, success)
• Add die, success, and info helper function definitions to the script
• Preserve existing script behaviour

Closes #641

Test plan

• Script runs without errors
• Output uses coloured → and ✓ indicators instead of bare echo
• Shell linting passes (shellcheck, checkbashisms)

[dnyw4l3n13]

Orchestrator review complete.

• CI: all required checks passed (build-pre-release ✓, pull-request ✓)
• Code changes verified: die, success, and info helper implementations in git/all-to-default-branch match the standard from shell-scripts.examples.md exactly
• All bare echo calls replaced with the appropriate output helpers
• CHANGELOG.md updated with the entry for this change
• No PR comments requiring replies
• PR is already marked as ready for review

[credfeto]

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