fix(runtime): suppress newline after EOF in prompt()

[murataslan1]

Description

When stdin is closed (EOF), prompt() was outputting an extra newline compared to confirm() and alert(). This inconsistency was caused by rustyline's internal terminal handling.

Root Cause

• prompt() uses op_read_line_prompt() which internally uses rustyline's Editor::readline_with_initial
• confirm() and alert() use readLineFromStdinSync() which is a manual byte-by-byte read
• When rustyline receives EOF, it outputs a newline as part of its terminal restoration

Fix

This PR adds an ANSI escape sequence (\x1b[1A) to move the cursor up after EOF is received, counteracting the unwanted newline that rustyline outputs.

Testing

# Before fix - note the newline after 'Prompt'
$ echo '' | deno eval 'prompt()'
Prompt 
$

# After fix - no extra newline (matches confirm behavior)
$ echo '' | deno eval 'prompt()'
Prompt $

Fixes #22956

[CLAassistant]

All committers have signed the CLA.

[Copilot]

Pull request overview

This PR fixes an inconsistency where prompt() outputs an extra newline after EOF compared to confirm() and alert(). The fix adds an ANSI escape sequence to move the cursor up one line to counteract the newline that rustyline outputs during EOF handling.

• Adds cursor positioning logic to handle rustyline's EOF behavior
• Maintains consistency with confirm() and alert() terminal output
• Includes documentation comment linking to the related issue

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[Copilot]

The expression editor.helper().map_or(0, |_| 0) always evaluates to 0 because the closure ignores its argument and returns 0 regardless of whether the helper exists. This makes the horizontal cursor movement sequence \x1b[0C effectively a no-op. If the horizontal positioning is not needed, consider removing it entirely and using just eprint!("\x1b[1A"). If it is needed, the logic should be corrected to calculate the appropriate column position.

Suggested change

	eprint!("\x1b[1A\x1b[{}C", editor.helper().map_or(0, |_| 0));
	eprint!("\x1b[1A");