feat: improve agent creation workflow and documentation

## BMB Agent Workflow Improvements
- Always create folders for agents (even simple ones)
- Add compact info-and-installation-guide.md (20 lines max)
- Include installation guide with every created agent
- Update workflow to use standalone_output_folder structure

## Documentation Updates
- Clarify --defaults makes installation non-interactive
- Update all parameter documentation for clarity
- Fix npm package references (bmad-method only)

## New Agent Structure
Every agent now gets:
  agent-folder/
  ├── agent-name.agent.yaml    # Source YAML
  └── info-and-installation-guide.md  # Quick install guide + description

## Quick Install Commands (added to guide)
- Interactive: npx bmad-method agent-install --source ./agent.yaml
- Non-interactive: npx bmad-method agent-install --source ./agent.yaml --defaults

This makes agent installation much more user-friendly and consistent.

docs/custom-agent-installation.md

@@ -46,7 +46,7 @@ bmad agent-install -s path/to/my-agent
 # Install a specific .agent.yaml file (simple agent)
 bmad agent-install -s path/to/my-agent.agent.yaml
 
-# Install with defaults (skip all prompts)
+# Install with defaults (non-interactive)
 bmad agent-install -s path/to/my-agent -d
 
 # Install to a specific destination project