Add pre-commit hook running precious lint

Checks staged files with precious before each commit. Enable with:
  git config core.hooksPath .githooks

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: oschwald

.githooks/pre-commit

@@ -0,0 +1,2 @@
+#!/bin/sh
+precious lint --staged

CLAUDE.md

@@ -62,4 +62,5 @@ src/
 
 - **mise** manages Node, pnpm, and precious versions (see `mise.toml`).
 - **precious** is the code-quality runner (config: `.precious.toml`).
+- **Git hooks** live in `.githooks/`. Enable with: `git config core.hooksPath .githooks`
 - GitHub Actions: test, lint, CodeQL, zizmor, release workflows.