[Mohamedajab]

Summary: Explain the hidden prompt, piped input and file input in sotto set --help.

Closes #596

Adds POSIX examples for the prompt, a complete file value and a synthetic printf pipeline. Explains that stdin preserves line endings and trailing newlines, is not dotenv import, and does not replace local setup or unlocking. Keeps the warning about credentials in shell history and adds process arguments to it.

Adds a focused Cli::command() help test. Input handling, storage and encryption are unchanged.

Validation:

• Checked the wording against Command::Set, read_value() and the existing help-test pattern.

• git diff --check passed.

• Rust/Cargo is unavailable locally, so I have not run the Rust test, rustfmt, or rendered sotto set --help. This is a draft pending those checks and a readability check of the rendered help. No real secrets were used.

• I signed off every commit (git commit -s / Developer Certificate of Origin).

[Maxerns]

Thanks for this, it covers #596 well. I checked the wording against read_value and the
Set path and it holds: no trimming on stdin, prompt by default, unlock still required, and
machine tokens genuinely do not apply here. I ran fmt, the new help test and the rendered set --help here and all is clean and readable.