Sub-issue: Document and test the short CLI alias

[dipeshbabu]

Parent: #2
Related: #1

cmdgraph is already defined as a console-script alias in pyproject.toml, but the user-facing docs still mostly show python -m commandgraph .... This sub-issue is for making the shorter path visible and tested.

Scope:

• Update README examples to show the installed commandgraph command and the short alias where helpful.
• Add a CLI test or smoke check that the alias points to the same CLI entrypoint.
• Avoid renaming the project in this issue; keep the naming discussion in "Why waste time say lot word when few word do trick?" #2.

Acceptance criteria:

• Docs no longer imply python -m commandgraph is the main day-to-day path after install.
• The short alias is covered by at least one test or install smoke check.