fix: replace raw echo with standard output helpers in git/update-dotnet-sdk

[github-actions]

Summary

• Replace custom die() implementation with the standard printf-based helper (coloured output to stderr)
• Add standard info() helper using printf
• Replace both raw echo progress messages with info calls

Changes

• git/update-dotnet-sdk: update output helpers to match project standards

Closes #650

[dnyw4l3n13]

Status Update

Implementation complete. Changes made in this PR:

• Replaced custom die() (bare echo) with the standard printf-based helper (coloured stderr output)
• Added standard info() helper using printf
• Replaced both raw echo progress messages with info calls
• All shell linting (shellcheck, checkbashisms) passes

CI checks are currently pending — stopping here until they complete.

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[dnyw4l3n13]

All CI checks passed. PR is ready for review.

• All required checks: pass
• Shell linting (BASH via Super-linter): pass
• No outstanding review comments or questions

[credfeto]

Super-linter summary

Language	Validation result
BASH	Pass ✅

All files and directories linted successfully

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[dnyw4l3n13]

All checks pass and no outstanding work remains. PR is ready for review.

• All required CI checks: pass (including BASH linting, changelog validation, secret scanning, build)
• Copilot Code Review: pass
• No CHANGES_REQUESTED reviews
• No unanswered human comments