fix: use static plugin spinner outside TTY

[mturac]

Issue for this PR

Closes#27908

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Uses a static plugin install spinner when stdout is not a TTY, so piped/non-interactive runs print one line per step instead of terminal control output. Interactive terminals still use the existing animated spinner.

(AI-assisted)

How did you verify your code works?

• bun test test/plugin/install.test.ts
• bun typecheck

Screenshots / recordings

Not applicable; CLI output behavior only.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

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[github-actions]

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