feat(runner): hooks (before/after)

[CalvinAllen]

Description

Run commands before and/or after tasks.

Proposed Syntax

build:
  before: echo "Starting build..."
  cmd: cargo build
  after: echo "Build complete"

# Or with multiple commands
deploy:
  before:
    - echo "Checking prerequisites"
    - ./check-auth.sh
  cmd: ./deploy.sh
  after:
    - echo "Deployed successfully"
    - ./notify-slack.sh

Acceptance Criteria

• Run before commands/tasks before main command
• Run after commands/tasks after main command (only on success)
• Support single command or array of commands
• Consider afterAlways for cleanup that runs even on failure