feat: implement missing ddx templates command

[mehdipiraee]

Summary

The README documents ddx templates commands that don't exist in the CLI implementation, causing user confusion and broken workflows.

Problem

The README clearly documents these commands under "Resource Commands":

ddx templates list         # List available templates
ddx templates apply <name> # Apply template to project

However, running these commands results in:

$ ddx templates --help
Error: unknown command "templates" for "ddx"

Documentation vs Implementation Gap

README Claims:

• ddx templates list - List available templates ❌
• ddx templates apply <name> - Apply template to project ❌

CLI Actually Has:

• ddx list - Lists all resources (templates, patterns, prompts, etc.) ✅
• ddx apply <name> - Apply any resource ✅

Root Cause Analysis

Looking at the codebase:

• ✅ ddx prompts command IS implemented (prompts.go, factory functions, registration)
• ❌ ddx templates command is NOT implemented (no templates.go, no factory functions)
• ❌ ddx patterns command is NOT implemented (no patterns.go, no factory functions)

Only the prompts resource command was actually built - templates and patterns were documented but never implemented.

Expected Implementation

Following the same pattern as ddx prompts:

1. Create cli/cmd/templates.go with:

   func runTemplatesList(cmd *cobra.Command, args []string) error
   func runTemplatesShow(cmd *cobra.Command, args []string) error

2. Add factory functions in cli/cmd/command_factory_commands.go:

   func (f *CommandFactory) newTemplatesListCommand() *cobra.Command
   func (f *CommandFactory) newTemplatesShowCommand() *cobra.Command

3. Register commands in cli/cmd/command_factory.go:

   templatesCmd := &cobra.Command{
       Use:     "templates",
       Short:   "Manage project templates",
       Aliases: []string{"template"},
   }
   templatesCmd.AddCommand(f.newTemplatesListCommand())
   templatesCmd.AddCommand(f.newTemplatesShowCommand())
   rootCmd.AddCommand(templatesCmd)

User Impact

Current Workaround:
Users must use generic commands:

• ddx list (shows all resources mixed together)
• ddx apply template-name

With Implementation:
Users can use documented, intuitive commands:

• ddx templates list (shows only templates)
• ddx templates show <name> (display template content)

Acceptance Criteria

• ddx templates --help shows help text
• ddx templates list lists available templates from library/templates/
• ddx templates list --search <term> filters templates
• ddx templates show <name> displays template content
• Commands follow same pattern as ddx prompts
• Error handling for missing templates directory
• Proper test coverage

Related Issues

This is part of a broader documentation-implementation gap:

• Missing ddx patterns command (separate issue)
• README needs to be aligned with actual CLI capabilities

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