fix(cli): show adk create --type in --help

[ktz03]

Summary

• Expose the existing adk create --type option in --help by removing hidden=True.
• Aligns CLI help with the Agent Config docs that already document adk create --type=config.

Fixes #6737

Testing plan

• Confirmed the option is defined in cli_tools_click.py and only hidden from help.
• After merge / local install: adk create --help lists --type with choices CODE / CONFIG.

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[ktz03]

I signed the CLA.

[ktz03]

Rebased onto latest main (was behind). Same one-line change: remove hidden=True from adk create --type.