Optimize Dockerfile generation guidelines and skeleton

[dot-agi]

Summary

• Add Dockerfile layer optimization guidelines to Claude Code prompts
• Update skeleton template to include --no-install-recommends and software-properties-common
• Simplify language runtime installation examples (Python, Node.js, Ruby, Java)

Changes

task_skeleton.py

• Add --no-install-recommends to base packages layer
• Add software-properties-common to base packages (enables PPA support without extra apt-get)

claude_code_runner.py

• Add "CRITICAL: Dockerfile Layer Organization" section with two-layer pattern:
  • Layer 1: Base packages (skeleton provides)
  • Layer 2: Language runtime (Python/Node/Ruby/etc.)
• Add formatting requirements (space before \, use --no-install-recommends)
• Update Python example to detect version from .python-version/pyproject.toml
• Simplify deadsnakes PPA pattern (software-properties-common already in base)
• Update Node.js, Ruby, Java examples for consistency