Update documentation for first-time users and fix outdated agent names

Major documentation improvements:
- Fixed all outdated agent names throughout README.md and GETTING_STARTED.md
- Updated agent references from old names (todo-keeper, changelog-keeper, setup-repository)
  to new names (keepaTodofile, keepaChangelog, setupRepository)
- Created comprehensive HELLO_WORLD_TUTORIAL.md with step-by-step guide for new users
- Added prominent tutorial links in README.md and GETTING_STARTED.md for better discoverability
- Updated Python version requirements from 3.8 to 3.9 in project templates
- Enhanced first-time user experience with clear guidance and working examples

Documentation now provides:
✅ Working commands that match actual agent names
✅ Clear separation between new users and experienced users
✅ Complete tutorial from installation to running code
✅ Proper guidance for scenario one (greenfield projects)

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

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

src/kaizen_agentic/installer.py

@@ -456,7 +456,7 @@ name = "{project_name}"
 version = "0.1.0"
 description = "A Python project with Kaizen Agentic agents"
 readme = "README.md"
-requires-python = ">=3.8"
+requires-python = ">=3.9"
 license = {{text = "MIT"}}
 authors = [
     {{name = "Author Name", email = "author@example.com"}}
@@ -479,14 +479,14 @@ where = ["src"]
 
 [tool.black]
 line-length = 88
-target-version = ['py38']
+target-version = ['py39']
 
 [tool.flake8]
 max-line-length = 100
 exclude = [".git", "__pycache__", "build", "dist"]
 
 [tool.mypy]
-python_version = "3.8"
+python_version = "3.9"
 warn_return_any = true
 warn_unused_configs = true
 disallow_untyped_defs = true