feat(cli): --non-interactive flag; prompts fail fast with exit 4

[DavidWells]

Split from #8300 (8 of 9). Stacked on #8329 — merge that first; GitHub will retarget this to main.

What

New hidden global flag --non-interactive (CI detection already gated some prompts). Any would-be interactive prompt now exits 4 with the prompt named and the exact flags that answer it:

$ netlify link --non-interactive
 ›   Error: Cannot prompt for input in non-interactive mode (CI or --non-interactive).
 ›   Prompt: How do you want to link this folder to a project?
No project specified. In non-interactive mode, you must specify how to link:
  netlify link --id <project-id> ...

Covers authentication, link, and monorepo workspace selection (which also gains a --filter/--cwd remediation hint).

Why it helps agents

A hidden prompt in a headless session means an agent or CI job hangs forever with no diagnostic. Exit 4 is instant, diagnosable, and the message contains the self-correction.

Testing

• New unit tests for the non-interactive detection and fail-fast helper; dev monorepo integration test updated to expect exit 4
• typecheck ✓ lint ✓ 410 unit tests ✓

[coderabbitai]

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✨ Finishing Touches

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