fix(ci): skip Lefthook installation in CI/Vercel environments

**Problem:**
Vercel deployments were failing during `pnpm install` because the `prepare` script tried to run `lefthook install`, which requires a git repository. Vercel's build environment doesn't have a proper `.git` directory, causing:
```
fatal: not a git repository (or any parent up to mount point /vercel)
Error: exit status 128
```

**Solution:**
Skip Lefthook installation when running in CI or Vercel environments by checking `process.env.CI` and `process.env.VERCEL` before attempting to install git hooks.

**Impact:**
- Vercel deployments will now succeed
- Local development still gets git hooks installed
- GitHub Actions CI will skip hook installation (not needed in CI)
- All previous tool execution fixes can now actually deploy

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

package.json

@@ -24,7 +24,7 @@
     "changeset": "changeset",
     "changeset:version": "changeset version && pnpm install --no-frozen-lockfile",
     "changeset:publish": "pnpm build && changeset publish",
-    "prepare": "node -e \"if (require('fs').existsSync('.git')) { require('child_process').execSync('lefthook install', {stdio: 'inherit'}) }\""
+    "prepare": "node -e \"if (!process.env.CI && !process.env.VERCEL && require('fs').existsSync('.git')) { require('child_process').execSync('lefthook install', {stdio: 'inherit'}) }\""
   },
   "devDependencies": {
     "@biomejs/biome": "^1.9.4",