Fix repl cursor multiline overflow

[Han5991]

Description

Fixes #59938

When multiline REPL input exceeds the terminal height, navigating the cursor with arrow
keys would move the cursor position correctly but fail to refresh the screen properly,
leaving stale content visible on the screen.

Problem

In the REPL, when a multiline input has more lines than the terminal height:

• Pressing UP arrow to navigate to lines beyond the viewport boundary
• The cursor position moves correctly
• But the screen doesn't refresh - old content remains visible
• This makes it appear as if the cursor "stops" at the top visible line

Solution

This PR implements viewport-based rendering in kRefreshLine() that displays only the
visible portion of input centered around the cursor position when content exceeds
terminal height:

• Near top: Show from beginning
• Near bottom: Show last N lines
• In middle: Center viewport around cursor

Changes

• Added rows getter to Interface class for terminal height detection
• Imported MathMin primitive for viewport calculations
• Modified kRefreshLine() to calculate visible line range based on:
  • Terminal height (this.rows)
  • Current cursor position
  • Total number of lines
• Adjusted prevRows calculation to account for viewport position

Demo

Before (Bug):

[Your video showing the bug - cursor moves but screen doesn't refresh]

After (Fixed):

[Your video showing the fix - screen properly refreshes during navigation]

Testing

2025-10-09.10.55.16.mov

Added regression test in test/parallel/test-repl-multiline-navigation.js that:

• Creates a 27-line input on a simulated 20-row terminal
• Verifies cursor navigation works correctly across viewport boundaries
• Ensures cursor position consistency when navigating up/down

Run tests:

./node test/parallel/test-repl-multiline-navigation.js
make test-repl

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.56%. Comparing base (bfc81ca) to head (315a793).
⚠️ Report is 193 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #60171      +/-   ##
==========================================
+ Coverage   88.55%   88.56%   +0.01%     
==========================================
  Files         704      704              
  Lines      208087   208120      +33     
  Branches    40019    40022       +3     
==========================================
+ Hits       184266   184318      +52     
+ Misses      15818    15808      -10     
+ Partials     8003     7994       -9     

Files with missing lines	Coverage Δ
lib/internal/readline/interface.js	97.38% <100.00%> (+0.05%)	⬆️

... and 30 files with indirect coverage changes

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[tarunbatra]

Appreciate you tackling this @Han5991.

Screen.Recording.2025-10-11.at.8.05.55.PM.mov

There are some issues in this implementation. the "viewport" based rendering scrolls the content before the cursor reaches the top. I don't think that's inline with other REPLs out there and users' expectations.

For example, Python's REPL:

Screen.Recording.2025-10-11.at.7.41.39.PM.mov

[tarunbatra]

We should only show the prompt on the actual first line of the content. Not the first line of the visible content.

[tarunbatra]

I am not sure what are we testing here. As I see, the cursor position always updated, but it's the visible content which did not.