Replace ConsoleUtility prompts with Spectre.Console (already a dependency)

[ChrisonSimtian]

Tier 1 — Replace. src/Fallout.Build/Utilities/ConsoleUtility.cs (~143 LOC) hand-reimplements interactive prompts — PromptForInput(), PromptForChoice() (arrow-key selection), ReadSecret() — with raw console state management.

Replace with

Spectre.Console — already referenced in Directory.Packages.props (v0.49.1). Use TextPrompt, SelectionPrompt<T>, and secret-masked prompts.

Why this is the easiest win

Dependency already present, the code is internal, and ~80 LOC of manual console handling simply disappears with better cross-platform behaviour.

Non-breaking

Internal utility — swap implementation, keep callers working. Target 2026 directly.

Acceptance

• PromptForInput / PromptForChoice / ReadSecret backed by Spectre.Console
• Manual Console cursor/key handling removed
• Setup/secrets CLI flows (Program.Setup.cs, Program.Secrets.cs) behave identically

From dependency-consolidation audit, 2026-06-02.

[ChrisonSimtian]

Insights from a discarded prototype (old paths; map to onion structure after #359).

• Spectre.Console already central (0.49.1) — just add the PackageReference, no inline Version.
• Wrap with TextPrompt, SelectionPrompt<T>, .Secret(); keep the 3 public static signatures identical (non-breaking).
• Scope is smaller than the issue states: the CLI (Program.Setup/Program.Secrets) already uses its own private Spectre helpers and does NOT call ConsoleUtility. Real remaining callers: CredentialStore (ReadSecret) and DelegateRequirementService (PromptForInput/PromptForChoice).