Proposal: Improve llama.cpp snippet

[ngxson]

In this PR, I propose some changes:

• Update binary name to llama-cli (for more details, see this PR: https://github.com/ggerganov/llama.cpp/pull/7809 and this homebrew formula)
• Add method to download llama.cpp via pre-built release
• Split snippet into 3 sections: title, setup and command
• Use --conversation mode to start llama.cpp in chat mode (chat template is now supported, ref: https://github.com/ggerganov/llama.cpp/pull/8068)

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Proposal for the UI:

(Note: Maybe the 3 sections title - setup - command can be more separated visually)