feat(cli): task arguments

[CalvinAllen]

Description

Pass arguments to tasks from the command line.

Proposed Syntax

greet:
  args:
    - name: name
      required: true
    - name: excited
      default: false
  cmd: echo "Hello, \${{ args.name }}\${{ args.excited && '!' || '.' }}"

Usage

./rnr greet --name=World
./rnr greet --name=World --excited

Acceptance Criteria

• Define arguments with name, required, default
• Parse arguments from CLI
• Interpolate in commands
• Validate required arguments