Fix the extra prompt and the dropped attributes in Command Line examples written in Markdown

[DmitrySharabin]

• A code block ending in a line break, as every Markdown code fence does, got one prompt more than it has lines: browsers draw no line after a final line break in <pre>. The plugin now sets that line break aside while it splits the code into lines, and puts it back. Code without a final line break behaves as before.
• The Bash continuation example in the docs lost all its attributes: no fence info string can hold data-continuation-str="\", since markdown-it-attrs reads \" as an escaped quote. It is now HTML, like the PowerShell example next to it.

Command Line blocks on the plugin page	prompts per block
before	4 4 9 20 none 7 23
after	3 3 8 19 10 7 22 (same as prismjs.com)

test:plugins: 41 pass. Each new test fails without its part of the fix.

🤖 Generated with Claude Code

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