Add security and git policies, make repo a model example

- Never commit secrets; comprehensive .gitignore with fetch URL
- Never force-push to main
- go mod tidy before committing
- make hooks target with Go repo detection
- Add .editorconfig, .prettierrc, .prettierignore
- Template files URL for new repo setup

Makefile

@@ -1,4 +1,4 @@
-.PHONY: test lint fmt fmt-check check docker
+.PHONY: test lint fmt fmt-check check docker hooks
 
 PRETTIER := yarn run prettier
 
@@ -19,3 +19,11 @@ check: test lint fmt-check
 
 docker:
 	docker build -t prompts .
+
+hooks:
+	@printf '#!/bin/sh\nset -e\n' > .git/hooks/pre-commit
+	@if [ -f go.mod ]; then \
+		printf 'go mod tidy\ngo fmt ./...\ngit diff --exit-code -- go.mod go.sum || { echo "go mod tidy changed files; please stage and retry"; exit 1; }\n' >> .git/hooks/pre-commit; \
+	fi
+	@printf 'make check\n' >> .git/hooks/pre-commit
+	@chmod +x .git/hooks/pre-commit