docs: use shell blocks for Docker commands

[Wenjunyun123]

Summary:

• Converts Docker command examples to copyable shell code blocks.
• Moves command output to a text block and removes prompt markers from commands.

Testing:

• git diff --check
• rg -n '^\s*$\s+' demos/docker_images.rst

Fixes #84

AI assistance: This documentation fix was prepared with AI assistance and reviewed before submission.

[arnopo]

same remark here for the commit message. you can also use the assisted-by for the IA

Assisted-by: [Agent Name]:[Model Version] [Tool1] [Tool2]