feat: add prek pre-commit hooks and dependabot (#1720)

* feat: add prek pre-commit hooks and dependabot

Pre-commit hooks (via prek):
- Basic hygiene: trailing-whitespace, end-of-file-fixer, check-yaml, check-added-large-files, check-merge-conflict
- Security: detect-secrets, zizmor (GitHub Actions audit)
- Linting: shellcheck, actionlint, oxlint, swiftlint
- Formatting: oxfmt, swiftformat

Dependabot:
- npm and GitHub Actions ecosystems
- Grouped updates (production/development/actions)
- 7-day cooldown for supply chain protection

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* docs: add prek install instruction to AGENTS.md

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

README.md

@@ -459,7 +459,7 @@ Use these when you’re past the onboarding flow and want the deeper reference.
 
 ## Clawd
 
-Clawdbot was built for **Clawd**, a space lobster AI assistant. 🦞  
+Clawdbot was built for **Clawd**, a space lobster AI assistant. 🦞
 by Peter Steinberger and the community.
 
 - [clawd.me](https://clawd.me)
@@ -468,7 +468,7 @@ by Peter Steinberger and the community.
 
 ## Community
 
-See [CONTRIBUTING.md](CONTRIBUTING.md) for guidelines, maintainers, and how to submit PRs.  
+See [CONTRIBUTING.md](CONTRIBUTING.md) for guidelines, maintainers, and how to submit PRs.
 AI/vibe-coded PRs welcome! 🤖
 
 Special thanks to [Mario Zechner](https://mariozechner.at/) for his support and for