Modularize CLI command handlers

[Mjboothaus]

Summary

• split CLI execution logic into dedicated modules under src/pdealchemy/cli/commands/
  • pricing
  • conversion (notebook/spec bridge)
  • validation
  • explain
• keep Typer command surface unchanged in src/pdealchemy/cli/app.py
• preserve existing CLI output and error behaviour while reducing app.py complexity

Validation

• uv run ruff check src/pdealchemy/cli/app.py src/pdealchemy/cli/commands/__init__.py src/pdealchemy/cli/commands/pricing.py src/pdealchemy/cli/commands/conversion.py src/pdealchemy/cli/commands/validation.py src/pdealchemy/cli/commands/explain.py
• uv run ty check src
• uv run pytest tests/test_cli.py tests/cli/test_notebook_to_toml.py tests/cli/test_spec_to_runtime_toml.py

Conversation: https://app.warp.dev/conversation/79aa7721-1947-44e5-840f-d20883bd8624
Plan: https://app.warp.dev/drive/notebook/eZQFltrUPlV50R8ZwHEybR

Co-Authored-By: Oz oz-agent@warp.dev

[semanticdiff-com]

Review changes with  

Changed Files

File	Status
src/pdealchemy/cli/app.py	37% smaller
src/pdealchemy/cli/commands/__init__.py	0% smaller
src/pdealchemy/cli/commands/conversion.py	0% smaller
src/pdealchemy/cli/commands/explain.py	0% smaller
src/pdealchemy/cli/commands/pricing.py	0% smaller
src/pdealchemy/cli/commands/validation.py	0% smaller