image push: respect NO_COLOR in aux notes

[WilliamK112]

Summary

• route docker image push aux-note coloring through tui.Output
• respect NO_COLOR when rendering the digest mapping note
• add a regression test covering terminal output with NO_COLOR=1

Why

Fixes docker image push emitting ANSI color codes in aux-note output even when NO_COLOR is set.

Fixes #6890

Testing

• added regression test: TestRunPushRespectsNoColorForAuxNotes
• local static check: git diff --check
• full Go test execution was not available locally in this environment because go is not installed in PATH here; CI should validate compile/test behavior

`docker image push` now respects `NO_COLOR`

[vvoland]

Thanks, your commit sign-off needs a real name though.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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