Adopt husky.net for contributor git hooks (dev-only, dogfood)

[ChrisonSimtian]

Summary

Adopt Husky.NET as a dev-only dependency
in this repo to manage contributor git hooks. Scope is the Fallout repo's own
developer experience — fast feedback before commit/push. This is explicitly not a
framework feature and ships nothing to consumers; it touches only .husky/,
Directory.Packages.props (dev tool), and contributor docs.

Why dogfood-only (and not a framework dependency)

Native git-hook generation from C# build targets — symmetric to the existing
[GitHubActions]/[AzurePipelines] generators — is the on-brand framework direction
and is tracked separately. Husky.NET overlaps with that model (its own
task-runner.json would be a second source of truth), so we are not taking it as
a framework dependency. Here it is purely a local dev-tooling convenience and a chance
to evaluate its cross-platform hook-install plumbing as prior art.

Proposed hooks

• commit-msg — reject conventional-commit prefixes (feat:, fix:, chore:, …)
  per repo rule Add CodeQL workflow for security scanning #7. Allow the ! breaking-change detection signal. This is a concrete,
  high-value guard we currently enforce only by review.
• pre-commit — fast formatting check (dotnet format --verify-no-changes or the
  build's Format target) on staged files.
• pre-push (optional) — a quick smoke (./build.ps1 Compile) gated to stay fast;
  skip full Test to avoid making push painful.

Tasks

• Add Husky.NET as a dev tool (tool manifest / Directory.Packages.props).
• .husky/task-runner.json with the hooks above; opt-in restore via
  dotnet tool restore documented.
• commit-msg conventional-prefix guard (the headline win).
• CONTRIBUTING.md note: how hooks install, how to bypass intentionally
  (--no-verify) when needed.
• Confirm Windows + Unix install both work (it's a cross-platform team).

Open questions

• Auto-install on first build vs. explicit dotnet tool restore (avoid surprising
  hook installation on clone).
• pre-push smoke in scope, or keep hooks to commit-time only for speed?

[ChrisonSimtian]

might be cool to run some stuff automatically before committing. We'll see, just a thought I had the other day