CLI: Add convenience aliases (pdd generate tests|examples|docs)

[gltanaka]

Summary

• Accept pdd generate tests ... as an alias to pdd test ... (and similarly for examples → example, docs → docs).

Acceptance Criteria

• Aliases dispatch correctly without breaking existing command names.
• Help text notes the aliases succinctly.

Implementation Notes

• Lightweight dispatch layer or hidden group to route to existing subcommands.

Credit: Rudi Cilibrasi

[keerthivasan2002]

Hi, I will be working on this issue and I will finish it around 28th sept 5pm Pacific Time

[keerthivasan2002]

Summary

Adds convenience aliases for common commands:

• pdd generate-tests ... → alias for pdd test ...
• pdd generate-examples ... → alias for pdd example ...

Motivation

Improves ergonomics by allowing a more natural command structure without breaking existing commands.

Implementation Notes

• Aliases are registered at the bottom of cli.py using cli.add_command.
• No changes to existing commands or logic.

[keerthivasan2002]

#76