Clarify the quick-start explanation

[MildyNora]

What changed

• Keeps the terminal lifecycle as the compact visual quick start.
• Moves the Anaconda comparison and safety/exit-code explanation into a dedicated How it works section immediately below it.

Why

This matches the intended README order while staying brief and avoiding a decorative animation that would not explain the agent workflow more clearly.

Validation

• Markdown diff check passed.
• The commands and exit-code descriptions are unchanged from the previously tested release.