Lean on Humanizer for standard string helpers; drop duplicates

[ChrisonSimtian]

Tier 2 — Consolidate. src/Fallout.Utilities/Text/String.* (~250 LOC) includes helpers that overlap Humanizer — already referenced (v3.0.1): String.Capitalize.cs (→ Pascalize/Transform), String.Truncate.cs (→ Truncate), String.Indent.cs.

Action

Delegate the standard string ops to Humanizer; delete the redundant helpers.

Keep (domain-specific — do NOT delete)

• String.Split.cs + String.KnownWords.cs — camelCase/known-word splitting that drives CLI parameter naming. No Humanizer equivalent.
• String.Quoting.cs — build/CLI-specific quoting.

⚠️ Breaking change

Public extension methods → breaking-change, experimental, batched to yearly major, CHANGELOG migration note. [Obsolete] forwarders where practical.

Acceptance

• Capitalize/Truncate/Indent delegate to or are replaced by Humanizer
• Domain-specific splitting/quoting retained
• CHANGELOG entry + migration note

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

[ChrisonSimtian]

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

• Humanizer already central (3.0.1) — add the PackageReference, no inline Version.
• Capitalize -> [Obsolete] forwarder to Transform(CultureInfo.InvariantCulture, To.SentenceCase). SentenceCase matches the old behavior (upper first char, keep the rest). Keep it: public surface + has Cake callers.
• Truncate/Indent (string overloads): zero non-test callers -> delete. Caution: Humanizer's Truncate has different ellipsis semantics, but nothing depends on it.
• Don't touch CustomFileWriter.Indent() (different method, returns IDisposable).