feat: Command timeouts

[lox]

Summary

Add command-level timeout support to prevent commands from hanging indefinitely in task pipelines.

Closes #1569

Usage

version: '3'

tasks:
  deploy:
    cmds:
      - cmd: npm run build
        timeout: 5m

      - cmd: ./deploy.sh
        timeout: 30m

Commands exceeding their timeout are terminated:

task: Failed to run task "deploy": task: [deploy] command timeout exceeded (5m): context deadline exceeded

Implementation Details

• Timeout applies per command, not per task
• Works with both shell commands and task calls
• Deferred commands use separate context and run even if parent times out
• ignore_error flag does not suppress timeout errors
• Zero/unspecified timeout maintains current behavior (no timeout)